Home Forums Hunting & Shooting Ask The Gunwriters Ask John Barsness Questions About "1-12 vs. 1-9 Twist in .223's"

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.