Hi Folks:

John Barsness's latest exclusive column, "1-12 vs. 1-9 Twist in .223's," should be in your inbox by now. If you haven't received this or previous versions, simply JOIN OUR MAILING LIST, and you'll be on board for future monthly columns.

Here are links to the last few columns:

"Modern Rifle Powders"

"Seating Bullets Straightly"

"Cartridges and Bullets for Whitetails"

"Rifle Cartridge Overall Length"

"The .300 Weatherby: The Best .30-Caliber Magnum?"

Don't forget to check out John's (and Eileen's ) other stuff at http://www.riflesandrecipes.com.

Thanks again, John!

"For centuries rifle shooters had been wary of using bullets that were too long for the twist in their barrels. This was because the bullets then became "over-stabilized," and accuracy went downhill." Emphases added.

Is that a typo for too short or for "under-stabilized" ?

FREX in the original 6mm Remington days it was said for game bullets - longer and heavier than the lighter varmint bullets - the shorter round nose was better stabilized and the too long spitzer was under stabilized?

Similarly at one time some accuracy advantage with medium weight bullets for the .308 Win over the .30-'06 Springfield was attributed to the 12 inch twist of the .308 Win and the failure of the .308 Win to handle the longest and heaviest bullets was attributed to under stabilizing with the slower twist.

Perhaps I misunderstand over and under usage?

That's a typo. It should have read too short.

The beauty of the Internet ... I'll fix it.

rb

Yeah, it's not like you just sent out 50,000 magazines!

I've got a new .223 Broughton bbl on order for my light-weight walking varmint rifle. It is a #3 contour bbl with a 12 twist. I intend to shoot 40gr-50gr bullets exclusively. Shots rarely exceed 250 yards. Is there any benefit to using a 9 twist?

I'm looking at building a .22-250 Improved, using a long neck by sizing down .243 brass and leaving it full length. I want to use a 60 grain solid copper (Barnes-type) bullet. This will be a spitzer boat tail, approaching the VLD profile. Will a 1:9 twist be fast enough, or do I need to go to 1:8?

So, what is the 1 in 7 twist in my colt upper good for? Or should I ask, why did Colt bother making 1 in 7 inch barrels for the M4?

John,

What's the heaviest bullet you've shot in a 1/9 223 Rem and out to what distance?

This was posted on Snipers Hide by Brian and I agree

Keep your 1:12.

I wouldn't go below a 50 grain bullet in a 22 cal, if you want to shoot 40 grain bullets get a 20 cal because they have a much high BC and achieve the same velocity.

I believe your accuracy will deteriorate with a 1:9 twist at the range and bullet weights you specify (more so for the 40 grain than the 50 grain). This is because it takes a while for the bullet to "settle down" in flight, like a football will start off with a small wobble but then stablise during mid flight (and then begin to wobble again toward the end of its flight). Below is a table that shows the approximate relationship between bore twist and bullet weight (based on using plastic tipped bullets in a 24 inch* barrel).

50gr 60gr
100 yards 1:12 1:12
200 yards 1:12 1:12
300 yards 1:12 1:9
400 yards 1:9 1:9
500 yards 1:9 1:9

Personally I have a 1:12 twist barrel and shoot 50 grain (foxes) and 55 grain (wild dogs). However if I was going to shoot 60 grain bullets exclusively I would go for a 1:10 twist. I don't think the 223 has enough grunt to push the 60 grain bullets fast enough. These are better left to higher powdered 22 centrefires (a 22-204 anyone?).

* John's article didn't talk about the assault weapon influence on twist rates. These weapons typically have shorter barrels and so obtain lower velocities, which require a faster twist rate to spin a bullet at the same revolutions-per-minute speed delivered from longer barrels. Therefore barrel length also needs to be considered (the longer the barrel the slower the twist should be). This explains why traditional 200 meter long-barrel target shooters chose the slow 1:14 twist for both 22 cal and 6mm bore sizes.

Matt

Most of the 20's 40 grainers don't have that meaningful of a BC advantage over the 40 gr NBT and the 223 will throw it faster than a 204 ruger using printed data.
Timely article though not the most in depth. Not that it was meant to be. Just an observation.

John,

Thanks for the article on the 223 and twist rate. I have read so much on the campfire about the 223 and deer that I would like to try the .224 on for deer hunting myself.
From you article I understand that a faster twist rate can stablize a heavier/longer bullet and also the short/ light bullets. You mentioned that your wife may try using a 22-250
for deer. Why the 22-250? Does the speed of the 22-250 change the twist rate required to stablize heavier/longer bullets or does speed play any role in that?
What is the standard twist rate for the 22-250?

Thanks
Keith

Let me start by saying again that, yes, velocity does have an effect on the twist required for any given bullet. I have gotten very fine accuracy with 60-grain spitzers in .22-250's and .220 Swifts with their standard 1-14 twists.

My wife is thinking of going to a .22-250 for as lot of her hunting because of several reasons:

1) She dislikes recoil more and more the longer she hunts.

2) She hardly ever shoots at more than 300 yards, even on pronghorn, and likes a flat enough trajectory that she can aim in the middle of the chest and hit the lungs. A .22-250 with a 60-grain bullet shoots just as flat more conventional "deer" cartridges out to 300 yards.

3) She knows from experience that it will do the job for most of her hunting, having used a .220 Swift some back when the 60-grain Nosler Solid Base was one of the best "deer" bullets. Nowadays we have even better .224 deer bullets.

The heaviest bullets I've used in 1-9 .223's have been boattails in the 70-grain range, and they have shot very well out to 600 yards. I also like to shoot 40-grain bullets, however, and do quite frequently, because of lower recoil and higher "lift" on prairie dogs at normal ranges. A 40-grain Ballistic Tip at 3700 or so is a very fine varmint load, except on windy days. Luckily, I have also found that most .223's will shoot various bullets weights to similar points of impact at 100 yards, so often carry handloads with various weights of bullets for different conditions.

The .204 with 40-grain bullets is indeed a little less susceptible to wind drift than a 40 in a .223, but not all that much. I also tend to take a .204 as well as a .223 when shooting PD's and have found that the .204, like the .223, tends to shoot different bullet weights to the same POI. Unless the wind is blowing I shoot lighter bullets in the .204, anything from 26-33 grains, again because I like the low recoil and "lift," but if the wind kicks up I switch to 40's.

I have never noticed any consistent difference in accuracy between 40-50 grain bullets shot in 1-12 or 1-9 barrels in a .223. That was one of the major points of the article. Somebody else may have had different experiences, but I have shot a LOT of .223's and while some rifles shoot better than others, I haven't seen bullet weight being the major factor.

Bryan at Berger really knows what he is talking about. He does more intensive research into what really happens with bullets at longer ranges than 99% of the people in the business.

JB...is Eileen thinking about using the 60 gr. Nosler or the 62 gr.TSX in the .22-250 , or whichever one shoots best for her....
Ingwe

The 60-grain Nosler Partition.

Great article JB!

So take it one step further

How about a 1 in 8? Surely 50gr+ will shoot great in a 1 in 8?

Specifically a Tikka 223 1 in 8 if I can find one...

The 1 in 7" twist of a mil spec AR is due to the 63 grain tracer bullet and it's length due to an 800M burnout requirement. 50's and 62's shoot just great in a 1 in 9 or a 1 in 8. Sierra thinks 70's shoot fine in a 1 in 8 or 9 too according to the box. I have seen 50's and lighter varmint bullets come apart from a 1 in 7" Delta HBAR Colt. 55 grain FMJ shoots just fine from them IME.

Not to get off track in this thread....but I've owned both an 1-8"twist 223AI and 1-8"twist 22-250. Both rifle's shot the 40 and 50gr Vmax's very well. 90% of the bullets fired through those rifles are 75Amax's though and I run them all the way out to 1000yds. I've burned up just shy of 4000 75Amax's over the past 2 years in those rifles so I've spent more than a little time behind them.

MuleDeer, thanks for writing that one, I enjoyed reading it!!!

Thanks!

Yeah, the 75 A-max would be one bullet that would require a faster twist, as they are LONG. I haven't been able to get them to shoot in any 1-9 rifle. But the most accurate load I've found so far in my semi-custom Remington 788 .223 uses the 69-grain Hornady BTHP. I have tried some 70+ Berger in the same rifle and they shoot OK but not great. I suspect that is pushing the edge with a 1-9, though I may just have not found the right powder yet.

MuleDeer, I "think" that the 1-9" is just borderline with the 75 Amax. I have talked to some guys who say that it will work in their rifles, others say they haven't been able to get them to shoot at all.

Do you think that tolerances on factory 1-9" twists vary enough that it could explain that?

I'm wondering about twist variation myself. I have a Model 700 LTR that is supposed to have a 9" twist and it shoots great with 75 grain Berger VLD match bullets on top of N140.

I bought 75gr VLD's, 75gr A-Max's, and 80gr SMK's off a guy who couldn't get any of them to run in his 1-9" SPS Tactical 20" rifle. My 1-8" does fine. I have found that my rifle has a real preference for the heavy bullets. 50-55gr bullets shoot MOA, but those long bullets shoot much better.

I bought the VLDs on a whim and they shot great with the first powder I tried.

My gunsmith is after me to quit playing around with the little 40-55 grain stuff. I think he wants to put a 7" twist Hart on my rifle.

Edit: I may just do it too. I have a 12" or 14" (not sure, old factory Sako) twisted 22-250 I can use to burn up my stock of lighter stuff.

The only time I've found a 1-9" twist to be "a bad thing" is when trying to use SPSX or Blitz bullets, the thin-skinned ones. If the bore is nice and smooth, no problems, but let it get some wear in it, and it will strip jackets to a fare-thee-well. Blue is a very pretty color, but I don't care to see it halfway to the target...........
I've owned 1-9" twist rifles that handled the Blitzes very well, and others that, brand new, wouldn't shoot them for beans. I like to use the SPSXs or Blitzes because of the price differences over the poly-tipped bullets, but that's the only real complaint I have with the fast-twist .223s.

What is really interesting here is that both a 20-223 (known as the "20 Practical") and a 223 push a 40 grain bullet at about 3800 fps. This is unusual because a larger bore normally produces a higher muzzle velocity, be in this case it doesn't. Therefore, given the same muzzle velocity, the superior BC of the (40 grain) 20 cal bullet will outperform the (40 grain) 22 cal bullet by an ever increasing margin as the bullets moved further from the muzzle. So the 22 cal 40 grainers are hopeless beyond 200 yards (they drop and drift too much and have little energy left). And if you have a 1:9 twist then accuracy with the 40 grainers will be questionable also.

The BC for a 20 cal 40 grainer (at 3800 fps) is about .280 and for a 22 cal 40 grainer (also at 3800 fps) is about .220, so anyone wanting to shoot 40 grainers over long ranges will be much better served by a 20 cal chambering. Sorry if this is disappointing for some readers but it is the truth! But fear not, just shoot 50 grainers through your 223 and all will be solved.

John,

Do you know the reason that Remington still uses the 1-12" twist as their standard (SPS, CDL, VLS) .223 twist rate? Seems that 1-9" twist (like Savage uses) makes a lot more sense, and Rem does put a 1-9" barrel on the VTR in .223.

Mule Deer,

Given that your wife shoots deer within 300 yards, have you considered a 6mm-250? These work great out to 300 yards with 80 grain bullets. This chambering seems to be gaining popularity thanks to lower recoil than the 243 win. Both barrel and case life are better and less powder per fps is consumed.

For similar reasons I suspect the 6XC will be adopted as a factory chambering in the not-to-distant future. The 243 is just too hard on barrels.

In regards to using 40 grain bullets in a 223, check drop and drift tables and compare it with a 50 grain bullet. You'll be surprised at the difference (even more so if you compare it with a 40 grain 20 cal).

I'll try to respond to all I can remember:

I do suspect that 1-9 is marginal for 75 A-Maxes, and some of stability also depends on the particular rifle. Sometimes a cut-rifled barrel will stabilize bullets better than one with the same twist but button-rifled. Also, I have seen variations in twist from what's listed. This used to be more common but still happens. One of the old .250 Savage 99's I have owned (I have owned 6-8) had a 1-15 twist, and wouldn't even shoot the 100-grain Speer, about the shortest 100-grain .25 spitzer made. I couldn't figure out what the problem was until I finally measured the twist. After that I did find it shot the 87 Speer very well.

I suspect Remington won't change to a 1-9 twist in .223's until they wear out their present tooling--and maybe not then. Ruger has evidently also gone to 1-9, so it probably will soon be the industry standard.

I shoot ALL bullet weights in the .223, and yes I am very much aware of how much less 50-grain bullets drift in the wind than 40's. I figure it is my job to try everything so I do. If I were limited to one prairie dog load for the rest of my life it would be 50-grain Ballistic Tips and 26.0 grains of TAC in the .223--but since I'm not limited I shoot everything. Usually I show up on a prairie dog town with a .22 Hornet (various loads, but mostly 40's), a .204 (various loads from the 26-grain Barnes Varmint Grenade to the 40-grain plastic tips), and a .223 (everything from 40-grain BT's or V-Maxes to the heaviest bullet that particular rifle will shoot). Oh, and a Ruger Mark II .22 pistl that shoots like a rifle, and a .17 HMR CZ 452. Then I will add something special, which can range from a .45 Colt Ruger Bisley to a .375 H&H with iron sights loaded with 220 Hornady flat-points. Or maybe my .45-70 trapdoor.

If anybody has problems with 40-grain bullets coming apart on the way to the target in ANY centerfire .224, 40-grain Ballistic Tips will cure the problem. I have driven them up to 4400 fps with various rounds and they have always held together--until they got where they were going.

Eileen has killed big game with a bunch of different cartridges, including the .220 Swift, .243 Winchester, .240 Weatherby, .250 Savage, .257 Roberts, .270 Winchester, .280 Remington, .308 Winchester, .30-06 and 12 gauge. (She thinks real magnums are silly, partly because she has never had any problem killing really big game (such as elk, moose, gemsbok, kudu, blue wildebeest, zebra, etc.) with the .270, .308 and .30-06. She has enough experience to know what she's doing when she picks the .22-250.

Ramblin_Razorback,

Remington understands that a 1:12 twist produces the best accuracy with 50-55 grain bullets at medium ranges. They also understand that a 1:9 twist produces the best accuracy with 60-70 grain bullets at medium and long ranges. Remington then chooses the twist rate for each model based upon what they expect the customer to use it for.

Sorry I'm not John.

Remchester,

I'm not an expert on the subject, but based on what I've read, I VERY seriously doubt you would see any appreciable difference in accuracy (precision) for 50-55 gr bullets with a SPORTER-weight barrel (e.g., in an SPS and CDL) with a 1-12" vs. a 1-9" twist. With the flexibility a 1-9" twist provides, I can't see any reason to cut a sporter-weight barrel in 1-12" twist unless it was cost-prohibitive to change your tooling at this time. I think Remington is just behind the times.

This will be my final post so as not to hijack the thread. Pressure tested data I've seen
20 Tatical /40's/3700/63,000PSI
204 Ruger/40's/3700/57,000PSI
223/40's/3700+/53,000 PSI
Reality,it's a bitch.
"22 cal 40 grainers are hopeless beyond 200 yards"
That is a gem. Ballistics are easy to skew and I realize the NBT is the best of the 40's in .224, not nesesarily the 20 but just to see how things play out with like bullets at high end published velocitites.
100 yd. zero 400 yards
204/20-223/40 gr. NBT/3700fps/-19.7 19.1 drift at 10 mph
223 3800fps/-20.4 20.4
223 50 gr. NBT/3500fps/-23 20.7

So, having .223's with 7, 8, 9, and (probably 10 or 12) inch twists, I've probably got it covered??

Along with 40, 45, 50, 52, 53, 55, 60 63....etc. grain bullets.

Just to note,

The Remington VTR comes with a 1/9 twist in 223.

So's the Remington XCR Compact Tactical. (What do you expect if it's called "tactical"?

I forgot to comment on the claim that 40-grain .224 bullets are "hopeless beyond 200 yards." I've shot a lot of varmints out to 400+ yards with 40-grain Ballistic Tips from a .22 Hornet, much less a .223, and the varmints all died when hit. My friend Steve Dogzapper (aka Steve Timm) prefers 40 BT's to any other load in his beloved .223 AI's, and once won the .223 division of a long-range prairie dog shooting contest with a shot of just under 700 yards. He made the shot with a 40-grain Ballistic Tip. I know this because I was also in the contest.

Good article. I've shot both, but never shot a heavy (69 gr. bullet) in a 12 twist. Done the opposite, though. I used to think you could spin a bullet too fast, say a Hornet at 2900 fps with a 9 twist and a 33 gr. bullet, but I no longer believe you can if the bullet is good, and most are. Handi Rifles have a 9-twist, I'm pretty sure.

Edited to add: bullets out of a 12 twist should rotate the same number of times regardless of caliber or forward velocity: i.e. one turn in every twelve inches, limited by the interior ballistics. Does this sound right? A 1:9 rotates a bullet 33% faster, which is considerable. But I don't think it's enough to "blue streak" a bullet.

Back in the day, the 17 Rem would blue streak occasionally. I've heard it said that this was because the bullet was rotating too quick from a whatever-the-twist barrel, but I think it had to do with bullet construction and the blow-up was due to a flaw in the jacket.

High Power match shooters usually prefer 1-7.7 twist to stabilize Sierra's 80 grain MatchKing. That bullet and the Hornady 75 grain Amax will not stabilize well in a 1-9. Neither bullet, by the way, can be loaded to fit in an AR15 magazine ao they are single loaded. Sierra 69 and 77 grain MatchKings are preferred for magazine length (2.26 inches).

1-7.7 shot 55 grain boat tails just fine in my AR15.

For awhile there was a fad of using 90 grain bullets for 1000 yards because the 75 and 80 grain loads would not remain supersonic at that distance. These used a 1-6.5 twist.

My M-70 Stealth has a Wilson 1-9" bbl and will shoot the 75 Amax very well up to 300 yards. I use a stiff load of VV-540, CCI 450 primers and load 30 thou. off. Shoots inside 1.5" at 300 yards.

My best game load is the 65 Sierra GK and 26.7 gr. of VV-540. Very accurate and has performed well on deer/antelope.

The 65 Sierra shoots very well in my LTR 223, and I may try it on a doe this coming season. I've shot it with Varget, but today the 68 gr. Hornady match bullet did so well on top of RL15 that I want to try that powder with the Sierra too.

John,
My .223 WSSM with a 1:9 twist stabilizes 75gr A-Maxes very well. 5/8" groups @ 1oo yards. My .22-250AI neede a 1:8. As you mentioned before, speed affects stabilization also. That being said I can see where a .223 Remington may not stabilize an A-Max, but might stabilize a shorter 75gr slug. I am considering building a 1:8 .223 WSSM as the 1:9 may be marginal for a 80gr A-Max. Ross Setfriends .22x284 had deformation issues with the rate of twist he used. That's why I think as speed increases rate can decrease a bit to avoid bullet defromation or destruction. Ross's 22x284 might have been fine with a 1:9 or even a 1:10 twist.
John Boy

My M700P (1:9) does great with the 69-gn Sierra, and seems to stabilize the 75 A-Max just fine, though I have not yet found "the load" with that bullet.

26" barrel...

You should try some N140, it really works with the 75 grain Bergers for me.

I believe the 204 was developed by the 222 Remington Magnum. I could be wrong, but it would have been the 22-204. Actually, it would have been the 20-222.

Dan360,

The 204 Ruger is the same length as the 222 magnum, but it has less body taper and a longer body and has a 30 degree shoulder in place of the 222 magnum's 23 degree shoulder. This gives the 22-204 about 5% more capacity over the 222 magnum (when measured below the neck) which equates to about 100 fps. In contrast the 22-204 has about 8.5% more capacity than the 223 which equates to an advantage of about 200 fps (at the same pressure). 200 fps makes a surprising amount of difference in trajectory and retained energy. The 22-204 is ideally suited to pushing the new 60 grain NBT (based on my experience with the similar capacity 5.6x50 magnum).

Note also that brass for the 222 magnum might not be available for too much longer. 22-204 case can be easily formed from 204 Ruger cases which will be available for a long time to come, and it is available from a wide range of manufacturers. Yes 222 magnum cases can be formed from 204 Ruger cases, but this is a little harder, and why not take advantage of the larger capacity 22-204? Here's to hoping that Ruger introduces the 22-204 as a factory chambering. Maybe they will base it on a longer case (like the 5.6x50 magnum) and call it a 224 Ruger. That would give it about 300 fps over the 223, enticing more shooters to upgrade.

Having said all that, the 223 will not be displaced from the AR-15 format because of OAL limitations. But at longer cartridge would do well in bolt actions.

You mean the 22-204 gets 3700+ with a 50-grain bullet? That's .22-250 velocity.

8.5% extra case capacity means about a 2.1% increase in velocity at the same pressure, which is a long way from 200 fps, assuming the 3500 fps or so the .222 Magnum is capable of with a 50.

Hi John,

You raise some interesting points about plastic tip bullets. Thanks.

However the improved BC of plastic tip bullets actually reduces the need for a faster twist barrel because flight time it reduced. So plastic tip bullets should be causing a trend to slower twist barrels, at least when compared to appropriate twists rates for hollow point bullets of otherwise similar design.

There are other considerations such sectional density, lead free bullets, and boat tail designs, but I believe it is the trend to longer bullets that has had the most influence on twist rate. The trend to longer bullets itself is driven by three forces, long range target shooting, increased deer hunting with a 223, and improved long range performance for military/tactical purposes.

The improved concentricity and structural strength of modern bullets allows the lighter and shorter bullets to be shot reasonably accurately though an 8� or 9� twist barrel at medium range. Many hunters still do most of their shooting between 100 and 200 yards with 50 grain bullets, so given that accuracy between 100 and 200 yards is typically worse with 50 grain bullets in faster twist barrels, so a wholesale move to fast twist barrels would be unwelcome by many.

I would love to read an article comparing the accuracy of a Remington Model 700 with 9� twist with a Remington 12� twist of equal length with 50 grain bullets. This might have already been done, I just don�t know where.

Sako and Tikka rifles are even offered with a choice of 8� or 12� twists in otherwise identical models! This is quite clever because the don't disenfranchise any customers. If they do eventually settle on one twist rate maybe they will adopt a 10" twist rate.

Matt

Mule Deer,

My measurements are based on external dimensions. So the actual internal capacity increase might be closer to 10%. That might still leave the velocity advantage at less than 100 fps based on your method. However your method might not hold true across all calibers, bullet weights, and powders.

After looking at a few handloading manuals and web sites it appears the 223 and 222 mag produce around 3400 and 3450 fps with a 50 grain bullet from a 24 inch barrel with maximum loads (using Winchester 748 among others). There are less data available for the 22-204 and 5.6x50 magnum but a couple of reputable sources for the 5.6x50 place it around 3600 fps from a 24 inch barrel. Given that the 22-204 has only about 1% (2% based on external dimensions) less capacity than the 5.6x50 then I estimate the 22-204 would produce close to 3600 fps. Interestingly, Winchester 748 produces only around 3500 fps in the 5.6x50 while Hodgdon Benchmark produces 3650 fps. Benchmark gives the highest velocities with all bullet weights in the 5.6x50 so it would likely be a good choice for the 22-204. Unfortunately I don't have any data for VihtaVuori powders for the larger cases.

For comparison, the 22-250 produces around 3800 fps with a 50 grain bullet from a 24 inch barrel. It is very hungry for powder though, it uses about 35% more. Something I really like about the 222 family of cases is that they put less pressure on a bolt face, and so a smaller and lighter action can be used than for the 22-250. For this reason I'm a big fan of Sako and Cooper Firearms. I just wish Cooper would introduce a model 51 repeater sooner rather than later!

In summary, I'd say the 22-204 has only 100 fps advantage over the 223 when using W 748, but when using H Benchmark the advantage stretches out to almost 200 fps. However W 748 does burn at a lower temperature which extends barrel life. So if barrel life is a big consideration then the 223 has an advantage there.

Remchester,

I have talked to the makers of plastic-tipped bullets, and they have all assured me that the plastic tip does "count" as part of the bullet length when figuring twist rates.

The 1/4 formula (any increase in powder capacity result in an increase of 1/4 that percentage in potential muzzle velocity) works in just about all cartridges, except at real extremes. For instance, when comparing the .22 Hornet to the .220 Swift, the ratio is about 1 to 3.5. But for cartridges as similar as the .222, .223, .222 Magnum and .22/.204 it certainly applies.

It is also not powder specific. It assumes that the top-velocity powder is used in each case, whether that is the same powder for the various or not. Benchmark also produces top velocities in the .223.

Generally people who load wildcats exceed this because they unknowingly load to higher pressures. Comparing one cartridge loaded to 55,000 psi to another loaded to 62,000 psi is not valid.

I think that they need to start making 223 Bolt actions in 1/7 or 1/8 (1/7.7) twist. There's a big difference in the way that a 77 or 80gr bullet flies at medium ranges (600yds) vs the 69gr bullet that a 1/9 will stabilize.
Maybe for varmint rifles 1/9 is a decent comprimise but I'd still bet if serious varminters had serious bolt guns with the quicker twist that would shoot the heavier bullets they'd use them more than the lighter ones. Or even better how about a 22-250 barrelled to shoot 77-90's? I think Seyfried did one.............................DJ

My 9" twist LTR has done pretty well with the 75 grain VLD Bergers I bought on a whim, but I haven't stretched them out very far. My range limits out at 300 yards.

Mule Deer,

Maybe the addition of a plastic tip does produce a small destablizing effect, but maybe the reduction in flight time more than offsets this. I wish John had discussed this.

It is still intriguing that Benchmark only equals the velocities obtained with W-748 in the 223, whereas with the 5.6x50 Benchmark gives a significant increase over W-748. One source, which uses the same pressure measuring technique across all loads, lists the data below.

223 W-748 3400
223 H-BENCHMARK 3525
5.6X50 W-748 3500
5.6X50 H-BENCHMARK 3675

It will be interesting to see how factory velocities compare if and when it is standardized.

I think it is important to understand that the concept of an optimal twist rate for each bullet at a given muzzle velocity still holds true. It's just that the goal posts have moved a little.

It is also clear that bullets can now be spun faster without deformation thanks to improved construction. However this does not mean that a bullet should be spun as fast a possible, because modern bullets, as good as they are, are still not perfectly balanced. Therefore for best accuracy a bullet should be spun only "fast enough" to keep it stable within its useful trajectory range.

For this reason I believe there is a future for both 12" and 9" and 7" twist barrels for bullet in the 40-55 and 60-70 and 75-80 weight ranges respectively.

Personally I don't think the trajectory of the 223 with bullets heavier than 60 grains is acceptable beyond 300 yards (and even that is a stretch) for general purpose varminting where the shooter doesn't have time to either use a rangefinder or take multiple shots at the same target.

Marketing departments are making the most of the Tactical hype. Once it dies down we'll all be shooting 55 grain bullets again, and there will be a lot of unwanted fast twist barrels and Tactical rifles (with their gargantuan scopes) on the used market.

"John" didn't discuss stability vs. flight-time with plastic-tipped bullets because he has never heard of such a problem, or encountered it in the field. John (who is me) has talked to the major bullet manufacturers about this and is extremely puzzled about what your point really is.

In fact "John" is growing more and more puzzled the more you post, because many of the things you have suggested (such as 40-grain .224 bullets being worthless beyond 200 yards) do not match his experience, in fact are so different from his experience that he wonders where you got yours.

The columns I write here are not intended to be all-inclusive essays discussing every nit-picky possibility of a subject. For one thing, I don't get paid enough to do that. For another, the members of the Campfire get to ask questions about the column, one of the good/bad things about writing for the Internet.

I've got an Internet buddy in Colorado who whacks P-dogs with a .223 regularly at over 500 yards. I think his longest is about 7xx yards. He prefers a 6mm for those shots, but takes what he gets, I suppose. He shoots everything from 60 to 40 gr. bullets and has assuredly made shots at WAY over 200 yards with the light-weight pill. In view of Remchester's post, I asked him on another forum about it, in fact.

I'm interested in the slow-twist, low-mass approach to a .223 as I have a couple with 12-twist bores and I'm bound to use 40-55 grain stuff. As for long range, about four or so years ago a shooter on the Army rifle team scored a possible at 1000 yards, 7 twist (IIRC) and a 80 gr. bullet that was just barely supersonic, but apparently barely was good enough. The guy who told this was or had been on the team, a Lt. Col. in the Army whose name I can't remember...a Korean-American who folks here might know. He was head of the Army Marksmanship Training unit at Ft. Benning at the time.

I've shot tons of 40gr B-Tips out of a custom .221FB rifle. At max velocity, not quite what a .223 can produce, the .221 & 40 grainers were quite accurate and killed reliably at distances out to 350yds or so.

However, I'm considering the 52gr A-Max in my new .223 when it arrives.

One other thing that may or may not be pertinent to high-volume shooters, my bud said he THOUGHT faster twists were harder on bores. Sounds reasonable, I suppose. He goes thru a barrel about every year or so.

Is the article posted somewhere on the 24hr site? I'd like to read it.

I'm shooting 53gr TSX bullets in my 1-12 Remington 223 and the group starts to open up past 200 yards. Any other 50gr bullet (especially BT or VMax) all plop in the same ragged hole at 200.

I'm wondering if the longer TSX bullets are just on the verge of being too long for the 1-12 twist...

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Gatehouse,

Yeah, it does sound like the 53 TSX is a little long for the 1-12, at least at the velocity you're loading it to. Which is yet another reason I prefer the twists in my rifles to be a little too fast rather than a little too slow!

Thanks.

Do you mean if the 53gr had higher velocity it should stabilize in the 1-12?

I might try the 45gr TSX's. See how thier accuracy is at 200 and 300 yards.

Yeah, it probably would. The problem is getting the extra velocity.

I'll just ram more powder into it. I hear the Remington action is pretty strong, I am sure it can stand some blown primers...;)

Yeah, I have blown a few primers in Remingtons myself. They never hurt anything, but you've got to clear the pile out of the magazine now and then....

No worries, I will use a Dustbuster with the slim nozzle attachment

John,

Thanks for a well written, timely article.

I shoot a fast twist upper on one of my hunting AR's. It is twisted 1:7 and is 20" long. It shoots 60 grain Vmax's into little, itty bitty knots with 25.5 grains Ramshot TAC.

I've a touch of time behind various .223's twisted various ways with similar bullets. My killing is mostly bigger stuff like fox, bobcats, and coyotes instead of prairie dogs.

My question to you, if you get a minute, is whether or not you have observed terminal damage varying by faster or slower twists with the same bullet.

My question results from a medium sample size the past few years of larger varmints and watching them take a 60 Vmax from this 1:7 at 2900 MV. Their "behavior" after the shot is quite different than a 1:12 shooting the same bullet. I'll just say the 1:7 animals die extremely fast. The bullet seldom exits, and 95% of animals are DRT. The terminal reaction of the 1:12 animals is not as impressive. Maybe coincidence, maybe 2 years isn't long enough to draw conclusions.

What say you sir?

Thanks...

I haven't shot a 1-7 very much so really couldn't say about it. But it would make some sense that bullets from a 1-7 would tend to expand more violently than from a 1-12.

Between a 1-9 and 1-12 there doesn't seem to be all that much difference, but the only 1-12 .223 we have left in the house is a varmint-weight Rem. 700, and the barrel is 26" long. It gets more velocity than my 1-9 24" 788 (a stainless E.R. Shaw rebarrel) and a LOT more than my 16" barreled Bushmaster carbine.

In the 700 my standard loads of 28.5 TAC and a 40 and 26.0 grains of TAC and a 50 get around 3850 and 3450, which is kind of cranking. The 788 gets 100-150 fps less, and the AR-15 gets 300-350 fps less, so that has to make a difference as well.

Thanks John...

One of the good things about the Vmax, I have found, vs. the BT is their ability to perform at lower velocities. Plus they're cheaper and more accurate, on average, for me. Slow a BT down and you'll get lots of exits, at least with 50's-60's. Slow a Vmax down and you'll still lots of goo. Anyways, back on topic.

Personally, I do think there is something going on terminally with my 1:7. It is not a bad thing...grin.

Thanks for the reply.

TAC is some great stuff.

I've got a 6x45 on the way. It will be 22" and be twisted 1:9. Ramshot strongly recommended I not use TAC in it to my dismay.

Thanks and have a great weekend.

http://www.24hourcampfire.com/newsletters/March_2009.html

Bruce

This is certainly an interesting thread, but there are a few statements that have been made which need to be disputed.

Remchester informs us that: �This is because it takes a while for the bullet to "settle down" in flight, like a football will start off with a small wobble but then stabilize during mid flight (and then begin to wobble again toward the end of its flight). Below is a table that shows the approximate relationship between bore twist and bullet weight (based on using plastic tipped bullets in a 24 inch* barrel).�
Really? I�ve never seen that and I have been shooting at very long distances for some time now. It certainly runs counter to my understanding of external ballistics. Perhaps Remchester could point us to some sites that buttress his claim. At any rate, the way I understand it to work is as follows.

The reason for a spin on the bullet in flight is to user the statically stabilization of the gyroscopic effect of the spinning bullet for it to remain point on in flight. When the bullet leaves the confines of the barrel, where it has been spinning around its center of shape, it encounters something called air resistance, a force that acts on the bullet and attempts to cause it to destabilize and have it spin around its center of mass. Air resistance also causes the bullet to shed its forward momentum and one way to (partially) mitigate this effect if to give the bullet an aerodynamic profile. The greater the aerodynamic profile however, the more unbalanced the bullet becomes. You can see that the bullet is very light in front, where the ogive is, and has more weight in the rear half of the bullet. This imbalance is what the spin is designed to counteract. So, the longer and more aerodynamic a bullet is, the higher the pin rate required to statically stabilize said bullet.

Now that we have that out of the way, let�s continue. As the bullet leaves the barrel, it has achieved two maximums (maxima?). The first one is its forward velocity, aka MV and the second one is its spin rate. The spin rate is a function of the MV and the twist rate of the barrel. For example, at 3000FPS, a 1:12 twisted barrel will produce a spin rate of 3000 RPS (revolutions per second,) or 180,000RPM.

As time advances, the forward velocity of the bullet will decreases according to various formulas. The main factors in this decrease are BC (ballistic coefficient, how �slippery� the bullet is in the air) and SD (sectional density, how heavy the bullet is for its diameter. The higher the BC and the SD, the less rapidly the bullet loses its forward velocity. Indeed, the SD is used in the calculation of the BC, but I like to keep both out in the open. The air may be more humid or colder or the barometric pressure may be higher or the elevation lower, and those things do affect the amount of resistance the air puts up to the bullet, but is does not make too much difference. The single biggest environmental element is temperature, provided the elevation is the same. So I guess you could say elevation is also a big environmental element. So the bullet loses forward velocity as time goes forward. The bullet also loses rotational velocity, but this is shed at a MUCH lower rate than the forward velocity.

Now, as the forward velocity decreases and the rotational velocity stays about the same, the destabilizing forces diminish, but the stability remains the same. The bullet will remain stable, and will actually become more stable as time goes on, all the way until one of two things occurs. 1- The bullet becomes subsonic and the transonic passage knocks it around. 2- The bullet arrives at its destination. The vast majority of bullets will go subsonic and not be affected. I am here to tell you that I have shot enough bullets at long range that went subsonic hundreds of yards from the target to know that to be true. On the other hand, there are bullets known for their transonic instabilities; the 30 cal 168gr SMK comes to mind.

To say that a bullet is unstable at the beginning of flight and then becomes stable further down is fantasy. A bullet may well be buffeted by the muzzle blast, but it is very stable if its spin rate is sufficient for it to be statically stable at the muzzle.

Gene L. then asks: �bullets out of a 12 twist should rotate the same number of times regardless of caliber or forward velocity: i.e. one turn in every twelve inches, limited by the interior ballistics.�
As long as we are talking about inside the barrel, that is correct but once outside, that ceases to be true. Bullet spin is a function of time, not distance, once outside the barrel. Let�s continue with our example of 1:12 twist and 3000FPS. At the muzzle, the bullet is turning over once every 12 inches, at 3000RPS. Let�s say it�s a mild-loaded 52gr SMK. It takes 0.11 second for the bullet to get to 100 yards; in that time it will have spun around 330 times. Since there are 300 feet in 100 yards, if the bullet really turned over once every foot, it would have done so 300 times by the time it got to 100 yards. At 500 yards, the travel time is .78 second which would have caused the bullet to spin 2,340 times. 500 yards is 1500 feet and if the 1:12 rule would have been followed, the bullet would have spun over 1500 times.

IndyCA35 says: �For awhile there was a fad of using 90 grain bullets for 1000 yards because the 75 and 80 grain loads would not remain supersonic at that distance.� While I have not been able to keep the 75gr A-Max solidly supersonic at 1000 yards in a .223, I have absolutely no problem doing that with the 80gr SMK or JLK. In fact, they arrive at Mach 1.2+.

Then Remchester makes the following statement: �However the improved BC of plastic tip bullets actually reduces the need for a faster twist barrel because flight time it (sic) reduced. So plastic tip bullets should be causing a trend to slower twist barrels, at least when compared to appropriate twists rates for hollow point bullets of otherwise similar design.�

I am sorry to say that I have absolutely no clue what is being postulated here. I fail to see the relationship between faster twist barrels and reduced flight time. As I explained above the longer and more aerodynamic a bullet is, the higher the minimum spin rate required to stabilize it. This is exactly the reverse of what Remchester is stating. Certainly my (and those of multitudes of others) observations have borne out the need for faster twist for the longer bullets.

I can fill in some detail in this story. I'm a Service Rifle Competitor, and one of the major drivers in the fast twist, heavy 224 story is my chose sport. I've also been trying to track the history of the AR/M16 as a Match Rifle.

Back in the 1960's, Rodman Lab of Rock Island Arsenal put out some Match AR's for Highpower Competition as a test. They shot wonderfully at 200 and 300 yards, but suffered from wind at 600 because the heaviest available bullets were somewhere around 63 grain (and Semi Spitzered IIRC). They used 9 twist barrels.

About the same era, the gubmint was researching extending the reach of the 223 with their SALVO project. Bill Davis Jr, the father of the VLD was involved in that project and sent me a couple of sample bullets. They were made by a small company in California that went on to become Sierra Bullets.

To my knowlege, the Rodman Project never met the SALVO Project.

Someone already mentioned the rationale behind using a 7 twist in the M16A2. The optimal twist for the SS109/M855 62 gr round was actually 1/9 according to the USMC Major in charge of the project, but the Tracer round required the faster 7 twist in very cold weather.

9 twists would have remained the fastest commonly available twist to shoot the 68's and 69's (and the 7 twist M16A2's would have remained an anomaly) if it weren't for the Service Rifle Competitors pushing the development of the M16 as a Competitive rifle. It was first the privateers like Bill Wylde and Jimmy Knox of JLK in the 80's and 90's. But in 1992 or so, the watershed event occurred. The USAMU (Army team) was mandated by their commander to set aside their Match M14's and develop and shoot the M16 in competition. Somewhere along the line, Sierra made 80gr 22's mainstream when they introduced their 80 Match King. In 1994, the Army ran the table and cleaned house winning big with their M16's versus the previously dominant M14.

Everything went black from there and we saw the introduction of the 75's, 77's etc.

The 90gr bullets are an interesting side note. Someone mentioned a clean score being shot at 1000 yards. Rost495 and I had a ringside seat to the development of the 90 shooting AR. They can work...very well. But folk seem to have trouble getting them to work consistently. The JLK 90's have won the Porter Trophy (1000 yard Service Rifle at Camp Perry). They've also shot the first clean at the Interservices 1000 yard Match with Chris Hatcher of the Army on the trigger). On paper they're wonderful. Yes they require a 6.5 twist. 7 if you push them very hard. (FWIW, FTR_Shooter, I've been of the mind that the upsetting/destabilizing forces increasing at a greater rate than the stabilizing forces of increased spin due to increased velocity. Unfortunately of late, the empirics seem to be overruling me and I'm an empiricist!)
They're largely out of favor these days because of inconsistent results and even the Army has shelved them last I heard.

Here's a bit more empirics. Hornady says "for 9-twist" on the box of the 75 Amax's. Similar to Mr B, most folk I know find they need at least an 8. Similarly, Sierra says at least an 8 for their 80's, but I and more than a few others own 9 twists that have stabilized them out to 600 yards.

I'm surprised I haven't seen a single reference to Greenhill (or was I just skimming too fast?)

ChrisF, nice post, thank you. A lot of people think they can make up for a lazy twist with higher velocities. This can work up to a point, but as you increase the velocity, you also increase the minimum required spin rate for a statically stable bullet. This is why you can actually get a 22-250 or a .220 Swift with a 1:9 twist actually stabilize bullets that need a 1:8 twist in .223. If one does the math, one can see that spin will increase substantially with an additional 400-500 FPS, but it won't make much difference with an additional 100-150FPS.

Of course one must also realize that by dramatically increasing the velocity and therefore the spin rate, one can actually run into the problem of dynamic instability that can be engendered by less than perfect bullets. In this day an age, this happens less than it used to due to greatly enhanced manufacturing methodology.

As was stated earlier, the increased twist creates higher internal pressure and can probably cause more bullet damage if the bullet does not engage without slipping.

As for Greenhill, he's so last millenium. And that formula is really aimed (pardon the pun) at cylindrical bullets or yesteryear and lower MVs. With today's incredibly aerodynamic bullets the formula needs tweaking. When I look at my 80gr JLK or the 180gr JLKs, I am simply amazed at how streamlined these bullets are, and they need a good twist.

The 75 Amax is my go-to bullet in my 223WSSM with a 1/9 Pac Nor. The bullet behaves beautifully down to 3250 (at 5,000 foot elevation).

Sounds like that bullet is right "on the edge" as far as stability is concerned with a 9 twist. FWIW, Dutch.

That makes sense in the .223 WSSM, with its extra velocity--and at that elevation.

I haven't yet gotten it to shoot consistently in a .223 Remington with a 1-9 twist--and at 4000 feet. It has teased me now and then, but....

At 3250FPS, in a 1:9 twist the spin rate of the bullet is 4320RPS. I know that I stabilized it properly in my 1:8 twist barrel at 2800FPS, with a spin rate of 4200RPS. As we can see the spin rate is virtually the same, however because the WSSM has a higher velocity, the minimum spin rate required to stabilize the bullet is somewhat higher but this required increase is tempered by the higher elevation. However, I would think the WSSM should be able to stabilize it in a 1:9 at sea level.

It would be interesting to work up some sort of chart where you can see the minimum required spin rate to stabilize any given bullet in a range of velocities. I don't think such a chart exists. But my guess is that at sea level, a spin rate of about 4000RPS should statically stabilize the 75 A-Max at velocities under 3000FPS.

To calculate the spin rate in revolutions per second, I use the following factors:

1:7| 1.7 * MV = xRPS
1:8 | 1.5 * MV = xRPS
1:9 | 1.333 * MV = xRPS
1:10 | 1.2 * MV = xRPS
1:12 | 1 * MV = xRPS
1:14 | 0.86 * MV = xRPS

As elevation increases, the 4000RPS figure will decrease, but I do not yet have an algorithm for that. As temperature decreases the 4000 figure will increase, and again I am not certain of the rate. Conversely as the temperature increases the value will go down.

And again, above 3000FPS in muzzle velocity, the 4000 threshold will go up, but I am uncertain of the rate. Empirically, I do not think the increase in minimum spin is a 1 to 1 relationship with the increase in muzzle velocity, I believe it is less.

Robert Rinker agrees with you. His calculations show that the overturning moment of the bullet increases slower than the increase in stabilization of the bullet by increasing muzzle velocity. In other words, stabilization increases with muzzle velocity (all other things equal), but the increase is smallish. FWIW, Dutch.

I am I the first person to ask...A .375 H&H on prairie dogs? Do you find anything left?

With conventional big game bullets of 260-300 grains the bullet often just puts a hole through them, though the bllets do start to expand. With 220-grain Hornady flat-points the result is much like a .22-250.

Chris,

Surfed in and found this thread. I have vivid memories of the early dayz with the .223 and all manner of twists and bullets.

The big problem (after early 1984) was having barrels made with enough twist to handle the bullets that were coming along at a furious pace.

Still have examples of many of these heavy bullets. Some are in marked boxes, but many are in plastic bags. I know what my children will do with that history....................

Best to all,
Bill Wylde

Wow! I am glad you found this thread. Folks...for any that care at all about this history, Bill Wylde was one of the integral parts of the equation. As I had mentioned, Highpower Service Rifle Competition was one of the major drivers of the development of the fast twist/heavy bullet AR Service Rifle. And Bill Wylde was one of the pioneers that set the stage for these things going mainstream. Under the handguard free float tube, the "Wylde Chamber" are just a couple of the innovations that have come out of that Mad Scientist Laboratory in Greenup.

Grandpa Yoda, I've been telling myself I owed you a call when things settled down on your end. I still have my notes from earlier conversations, and hope to add more from your recollections. Don't let your kids throw those bits of history out! Slip a note in the bags that they're worth something to a crazy HP Shooter.

p.s. If any of ya'll have heard of a "Tube Gun" that some of the Long Range folk have been playing with...you can thank Bill Wylde for that one too!

One thing I forgot to mention that underlays post from myself and others is that some of the range and velocity figures mentioned for the 223 heavies is out of a 20 inch barrel. The AR Service Rifle has a 20" barrel which you could imagine puts some limitation on how fast you can drive 75's and 80's. It's more or less a convention that a Sierra 80 won't stay supersonic out to 1000 yards with normal sane pressures out of 20"...hence the move to 90's and other VLD designs. I think that explains some of the differences in experiences posted.

Thanks for the intro, Chris.

Shot some of the JLK 90's through a 30" 6.5" twist Krieger F-Class rig just last week. I could not believe what I was seeing. Those bullets produced bugholes at 100 yards!

Please feel free to call any time.

Here's one for the crowd and John. I'm running a Swiss Arms Black Special 223 (similar to the SG 550) with a 1:10 twist and a 20" barrel. I imagine that once I get started handloading for it I'll have some issues stabilizing bullets for a 1:9 twist due to not driving them quite as fast as I could with Clarke (Gatehouse)'s self depriming M700. So that leaves me in a bit of a no-mans-land with what is essentially an oddball twist. Should I take a step back with bullet weight and stick somewhere in the 64gr Berger FB range of things or is there some hope with stuff closer to 70 gr? Has anyone used a semi with a 1:10" twist and can shed a bit of light for me? The main problem up here is I have about as much access to components as Phil Shoemaker, making accurate shopping lists critical.

Corben

Late to this thread... but SHHHH... dont' tell folks about the 90 jlks, they are junk. Dno't work. Won't beat anyone. No advantage. Etc..... Chris F agrees too....

Good luck! Grins... OH BTW, I"m told for what you are doing an 80 smk around 2750 MV should be the best bet.... hahaha.

Jeff

I ran a 10 twist some years back. Long story there. 69s were ok. 70 jlks were ok. Hadn't heard of Bergers at that point. 75 jlks did not work. JLK had something under 70, IIRC that was ok too but I dont recall what it was.

If you want some 75 jlks and I can find some laying around I'd send em to you as a test. Also if you don't have access to 69s for a test I'm sure I still have open boxes of them here..

64 bergers should run super though. Of which I may still have a few too.

PM me...

Jeff, there's no need to whisper; you can have all the 90JLKs you want, I am quite satisfied with with the 80s myself.

Yep, you stay that way, very nice. I"ll take the extra couple inches or so on wind drift and your almost scratch 10s will be solid inner 10s for me...

But those 80 jlks were a great bullet and probably still are. If you moved back to an 80 smk then I'd have more of an advantage.

Actually truth be told in your game, and with the allowance of a long barrel, there may not be any difference, I"d have to know how fast you can push an 80 vs a 90 and then if accuracy was the same its a no brainer calculation.... all I can say is the AMU used the 90s to do the first ever clean at 1000 with a service rifle and it had never been done with an M14. Or with an AR and 80s. That at least says something about the bullet.

Corben-- what speeds are you getting from the Krieger? I had issues with them producing pressure before speed until I went to the 3 groove PN tubes. Never thought they were as good a tube as Krieger but they were good enough for me at least.

Jeff

Issue with the 90s is the fast twist required which increases the pressure more than whatever advantage you may get from the extra BC/lower velocity. In other words, I think you have to cut back on the load because of the twist and that takes too much velocity away.


And I know I'm going to get toasted for this one, but I never considered the M1A/M14 an accurate enough rifle for the long range, especially with the bullet weights with which it was saddled. The M16/AR-15 knocked the snot out of that rifle.

But The M14/M1A is an elegant weapon.

That is a question I had too - when I switched to using a 1-9" 16" bbl AR15 after years of using the usual 1-12" 22" bbl Model 70 on jackrabbits. Now jackrabbits are a bit bigger than PDs, and I was wondering if lopping off 200 fps (chronographed) using the same 55-gr Hornady SP would really cut down on terminal damage and the "red mist" effect. I had also been using a Rem 788 .222 with 50-gr TNTs as well which was slightly better than the stiffer 55-gr Hornady in that department.

Turns out I had nothing to fear. The "slow" velocity, but fast-twist AR load, if anything, seemed to to more damage. It also seemed to beat the TNT .222 by a hair perhaps. In fact it was only when I went to 40-gr BTs in the 1-12" bolt rifle that it slightly edged out the effect of the slow 1-9" on impact. So I chalked it up to the faster twist keeping the bullets explosive 200 fps slower.

And yes - those 40-grain Ballistic Tips did lose stability - as soon as they hit varmint flesh no matter what the yardage!

FTR_Shooter, can you describe what this statement is based on? You have data somewhere?

Absolutely. Let me see if I can explain it to you. I�ll do this in point form, so bear with me.

1- Pressure is created by the combustion of the propellant in the case. The pressure curve changes over time as the bullet leave the case and moves down the bore. As the distance between the bullet and the case grows, the pressure drops. The pressure drops to zero when the bullet leaves the barrel and the gases expend themselves in the atmosphere.
2- The pressure in the cartridge and bore is also accompanied with high temperatures; this is actually a combination that goes together; heat and pressure. The gases that are produced by the combustion of the powder are hot.
3- The longer maximum heat and pressure is maintained in a barrel the more damage is done to the barrel.
4- A 90gr bullet has a higher mass that an 80gr bullet, 12.5% higher to be exact.
5- An object with a higher mass requires more work to move it than is required to move an object with a lower mass.
6- Given the same force acting on two objects, the one with the higher mass will accelerate more slowly than the one with the lower mass.
7- One way to reduce the extent of the time under maximum pressure is to reduce the initial pressure, in other words reduce the amount of powder in the case.
8- Lower initial pressure means less generate velocity at the muzzle.
9- The 90gr bullet needs a 1:6.5 twist rate.
10- The 80gr bullet needs a 1:8 twist rate, I use a 1.7.75 twist rate.
11- In the 20 inches of barrel, the 90gr bullet will do 3.1 turns, the 80gr bullet will do 2.5 turns. The 90gr bullet will do 20% more turns.
12- A higher twist rate in a barrel creates more work to push the bullet through.

So, we have a 12% heavier bullet that needs a 20% faster twist rate to stabilize. Let�s see what we get for the longer barrel time and longer pressure curve engendered by the use of the 90gr bullet.

1- The claimed BC of the 80gr JLK is .510 and the BC of the 90gr JLK is .580. This is a 70 point difference.
2- The velocity of my 80gr JLK is 2860. The Hodgdon site shows the maximum velocity of the fastest 90gr bullet to be at 2530FPS and the 80gr to be at 2870. This is a difference of 340FPS.
3- The pressures are the same at about 52,000PSI.
4- According to JBM, the 80gr JLK will drop 30.8 MOA, take 1.531 seconds to reach 1000 yards and will be going at 1359FPS at the target. A 10MPH wind will need 8.2 MOAs to compensate.
5- According to JBM, the 90gr JLK will drop 37.9 MOA, take 1.678 seconds to reach 1000 yards and will be going at 1289FPS at the target. A 10MPH wind will need 8.3 MOAs to compensate.


I know that the USAMU uses the 90gr Sierra (with a lower BC than the JLK.) The higher pressures dictate they only use the case one time. I am using my LR load cases over 5 times.

The 80gr JLK in my 1:7.7 twist barrel goes faster and gets to 1000 yards before the 90gr JLK and requires less windage adjustment. The 90gr JLK will be 74.3 inches lower than the 80gr bullet at 1000 yards. On the other hand, to make up for its lesser performance, the 90gr bullet will be in the barrel longer and create more damage at the throat.

FTR_Shooter,
Thank you for indulgence in my question. Thank you too for the work put into your response.

Your points 1 through 11 are good background for those that might have just walked into this thread. What I'd add is that the bullet engraving force and the bullet jump to the leade are some other variable that come into play.

It's your point 12 however that bears more discussion and was actually the crux of my intial request.

Yes, a faster twist does take more work to move a bullet through. However this incremental work is not as great as you or the internet chatter would believe.

Harold Vaughn in his book "Rifle Accuracy Facts" derives spin up torque in his discussion on bullet core stripping/failure as a contributor to inaccuracy. (see pp 158-160). He uses the example of a 68gr 6mm bullet at 50Kpsi out of a 14 twist and a 65 gr 6mm bullet out of a 10 twist at the same pressure. The spin up torques were approximately 7 and 9 inch-pounds respectively.

Rinker does similar in his book "Understanding Ballistics" (pp131-133) and follows his derivation with the following statement:
"That is a lot of mathematics and work to show and prove the energy required to rotate the bullet is very small. Extremely small. If an example is worked out, it will fall in the general area, depending on the cartridge, twist, etc. of between 1/4% and 1/2% of the available energy. The loss in velocity, compared to a barrel with straight rifling (no twist would be even less."

Since I've earlier mentioned that I'm more of an empiric, I can actually share some of my experience measuring pressures in a 223 via Strain Gauge. I actually set up a strain gauge on a dedicated AR Upper to help work up loads for the 90gr JLK in a 6.5 Twist AR Service Rifle. The 90's were around for a few years but no one really wrung them out in a Service Rifle until John Holliger paid Pac-Nor to grind a 6.5 twist button. I got one of the barrels from the first batch (previously 7's worked, but were marginal and inconsistent).

Through the course of my instrumented testing, I found that you could get useful velocities out of a 20" barrel, standard 223 and 90gr JLK's at normal pressures. IIRC the bar was a 80gr SMK at 2750, and the 90 JLK beat that for wind drift at somewhere below 2500fps. I ultimately got them to better than 2600fps at decent pressures. I know that Rost495 was pushing them significantly harder with good accuracy.

Here's where your statement didn't match my experience: I was able to shoot 80gr Sierra's out of that 6.5 twist AR at comparable velocities to everyone else's 8, 7.7, 7 etc twist barrels at good pressures. There wasn't your theorized increase in pressure compared to the slower twists.

I took a look at the Hodgdon site and at first glance, and the 90 SMK's were significantly slower than the 80's with same powder similar pressures. Here's where it get's interesting. There were a few missing pieces from the load data, so I called Hodgdon and spoke to one of their techs who told me that the barrel configuration for all of their 223 load data is a 24", 12 twist with a SAAMI minimum chamber. I pointed out that the 80's and 90's require a faster twist for stability to which he responded they were only concerned with the internal ballistics and not the accuracy or external performance of the loads. Also significant was the 80SMK pressures were captured via Copper Crusher and the 90SMK's were done with Piezo. I'll leave it to Mr Bramwell and Dr Oehler to discuss how the two correlate, but I can say it wasn't an apples to apples pressure comparison.

So the Hodgdon data ends up being evidence against your statement. Hodgdon apparently feels the faster twist is insignificant for their load data because they're ignoring any potential liability created by shooters using the load data in a faster than tested barrel.

So why do I think the velocities on the 90's are lower? You got it right with the greater weight. Add to that my earlier mentioned engraving force. The longer bearing surface is much more significant than faster twist.

Not many who shot them extensively will say that the 90gr JLk's were inferior in the wind to the 80gr Sierra's or even JLk's. The problem was and continues to be getting them to shoot consistently...all the time.

ChrisF, I enjoy these discussions. They make me think and dig and reassess my understanding of how things work.


To my mind, there are three aspects to ballistics: internal, external and terminal. External ballistics are fairly easy to observe and measure and the various formulae are well-known. Terminal ballistics are not interesting to me; all I ask of my bullets is that they make a hole in the paper when they get to the target. Internal ballistics is an area in which I am still learning. The issues there are observations and measurement methods.

You refer to yourself as an empiric; I suspect you actually meant an empiricist, the definition of which refers to someone who believes that experience is the only source of knowledge. As you can plainly see, I am not a ballistician; I am a competitive shooter with a penchant (that�s a fancy word for �inclination� for those of us in La Grange,) for scientific explanation on my understanding of ballistics. So, one might say that I am a proponent of the scientific method to explain things.

I reread my original post where you point out the statement about which you are asking for further explanation. Let me repeat it here for simplicity sake.

�Issue with the 90s is the fast twist required which increases the pressure more than whatever advantage you may get from the extra BC/lower velocity. In other words, I think you have to cut back on the load because of the twist and that takes too much velocity away.�

Several days after I made this statement, I absolutely see where it is easy to misunderstand it and it actually is not well stated at all. One could actually see that statement and think I am saying the reason the 90gr bullet has a lower MV than the 80gr bullet is only because of the higher twist rate it requires. And that would be totally wrong. In my response to your query, I placed much more emphasis on the 12.5% weight increase as the main reason for the lower MV, and I believe you agree with me on that.

My point 12 does not have a measurement, because I do not know how to measure it, or even what to measure, but I believe that it is there. The scientific method requires that I come up with a hypothesis and present ways to prove or disprove this hypothesis, unfortunately at this time, I do not have such, only a belief that you don�t get something for nothing. I believe that a faster twist rate presents more resistance in a barrel to the passage of a bullet that a slower or even non-existent twist rate, I just don�t know what that is. So you can only imagine how interested I was in reading your well thought out response.

You are absolutely correct about the greater bearing surface of the 90gr JLK as opposed to the 80gr and I kick myself for failing to bring it up. In my defense, I will say that I composed my earlier answer in my hotel room after a long day at a customer site. The 90gr JLK has a bearing surface of .415 inch and the 80gr JLK has its surface as .340 inch. That is an increase of .075 inch or 22% over the 80gr JLK. Just to verify, the formula to calculate the actual bearing surface is Sb= (2 pi r)*h, where r is the radius of the bullet and h is the bearing length. So for the radius of .112 (half of the .224 caliber, the 80gr bullet with its bearing length of .340 inch has a bearing surface of .239 square inch. The 90gr bullet with its bearing length of .415 has a bearing surface of .292 square inch and increase of .053 square inch or 22.2%.

If I were to come up with an hypothesis for measuring the impact of the twist rate on bullet travel or resistance to travel, I suspect the bearing length of the bullet would be a factor in that equation. But that will have to wait for another time.

Thanks again for a very enjoyable discussion.

I generally try to keep things simple on my prairie dogs excursions - I shoot 40 gr BTs or V-MAxs in both my .223s (a Savage 20-inch varmint and a CZ-527 American.) I shoot 55 gr BTs in my Kimber Varmint .22-250 and I shoot 75 gr V-Maxs in my Tikka .243. I have had pretty good luck with the 40 gr in .223 out to about 300-350 yards.

IMO, the big advantage of the AR's for hunting is for coyotes, since u can get multiple shots off quickly if more than 1 comes into a call. Awhile back i was interested in trying to find out the effective range of the 223-based cases on them. The bullets i finally settled on were the JLK Low Drags, 52, 60, and 65, since they have the highest BC's available for their respective twist rates--

52/14 twist/BC-.302
60/12/.339
65/10/.395

My 9-twist ISSI .223 AI AR drives the 65 @ 3050, and shoots great at 400 and 500 yds. I've probably taken 30 coyotes with it and have had good results so far, but i need the DPMS VLD magazine and bolt stop (lost my only bolt stop). Hard to find those these days, since DPMS quit offering them (i heard the guy died who was making them..?). I think the 75 or 80 A-Max would also be good to those ranges if the VLD mag was used, just never shot 1 at 400-500 yds. with them yet.

Be interesting to hear others comments on the effective hunting range of the AR 223-based cases...?

I recently bought a Model 700SPS wit 1/12 twist in 223. I am interested in shooting either the 60 Gr Partition or the 55 grain TBBC. What are your thoughts on how this would perform?

My experience is that while accuracy may not be great with either bullet in a 1-12 twist, it should be adequate, and either bulet will work quite well on game.

Thanks John.

What length barrel?

24"

That makes a difference in my experience. You will be able to get a higher muzzle velocity which will generate a higher spin rate on the bullet and you should be able to get full static stability with the 60gr Partition and the 55gr TBBC. I would get a box of either one or both and try them out. My guess is that you will be very happy.

Do be aware that they may perform less well when it's cold and dry outside, but in MS, that should not be a problem.