Home Forums Hunting & Shooting Custom Rifles & Wildcats 7mm-08 ackley improved

OK. I guess i have stirred up a stink around here concerning the barrel length a 7mm-08imp should have. Lets start with some basics first. Velocity in relation to barrel length. The velocity of most 140 grn factory loads in this caliber is around 2800fps or 2900fps. These figures are reached firing these loads through a 24" test barrel. For every inch of barrel you add you will gain 50 to 100 fps of velocity. For every inch you take away you will lose about the same. These figures will vary slightly with different powder and bullet combinations. Also velocity gain stops at 27". Anything out past that is added weight you dont need. Now, why make the round an ackley improved? This is done for a couple of reasons. First is to increase powder capicity. Why increase powder capacity if you dont want more velocity? Unless you need to spend extra money for a tax write off or something. Next reason is accuracy. The expanded case, sharper shoulder, and shorter neck contribute to accuracy. A poster in another thread made it sound like I thought Kenney Jarrett was stupid for putting 22.5" barrels on the imp's they build. They do that because they can get better accuracy from the short barrels and that is what sells Jarrett rifles. Accuracy. They may be able to get back close to factory velocities with the shorter barrel but I promise you they arent pushing 140 grain bullets almost 3200 fps from them. This is possible from a 26" barrel. I had the factory barrel on the Remington that later became my first custom rifle reamed to the improved. All I could get out of it was 3000 fps. That barrel was 24" long. When I put the 26" tube on my velocity stepped up to 3185fps. Granted the longer barrel allowed me to use a little more powder in my loads but only like 1 or 1.5 grains. My loads with the 24" barrel used 44.3 grains of powder and the loads in the 26" barrel used 45.5. So what would you use on your improved? A shorter barrel that will cost velocity(the reason for making it an ack. imp. in the first place) or a 26" barrel that will make the ack. imp. really perform? And yes great accuracy is possible with the longer barrel when you find a powder, primer, bullet combination it really likes. Mine produced some groups at less than .4 with a barnes bullet nonetheless.

You largely rattled on upon topics you've little grasp of.

Quit while you're behind and call it a day................

OK Einstein lets hear how it really is then.

WT,
You are obtaining really high velocity for a 7-08AI even with a 26" barrel. I am wondering if the XLC coating is adding to your high fps readings. I've worked with several 7Mags sporting 24-25" tubes and have never reached over 3300fps with conventional 140gr bullets. I admit to little experience with these blue bullets but after I saw what Barney can do with em (3370fps) I can't but feel that blue coating has added to your higher readings in the 7-08AI.

I am going to try out these blue meanies in my 7-08AI. I have all the components you listed for your 7-08AI, 140XLC load at 3185fps. This will be interesting for sure! <img src="/ubbthreads/images/graemlins/grin.gif" alt="" /> Give me some time as I have a whole lotta projects going on! MtnHtr

First,you wanna tread lightly,upon things you don't savvy. The more you yack,the more you reaffirm your ignorance.

I shoot the 7-08 in a herd of combos that range from a 14" barreled XP-100,to a 24" barreled rifle. Betwixt those extremes,are 20's and 22" tubes.

You tout that such a cartridge will lose or gain 50 - 100fps,per inch of barrel length up to 27". My XP will push moly 120v-max's at 2750fps. I ASSURE you my 10" longer barreled 24" rifle,will not gain 1000fps of velocity,with that projectile. Though a 7-08 that pushed 120's at 3750 would interest me much. Bet your ass,that one wearing a 26" tube won't yield 3950fps. Might you see some light?

Then you babble such nonsense,as the following: "I had the factory barrel on the Remington that later became my first custom rifle reamed to the improved. All I could get out of it was 3000 fps. That barrel was 24" long. When I put the 26" tube on my velocity stepped up to 3185fps. Granted the longer barrel allowed me to use a little more powder in my loads but only like 1 or 1.5 grains. "

I ask simply. WTF?

Going from a 24" tube,to a 26" tube yields a 1 - 1.5gr case capacity increase? That as a minimum,is an extry grain of propellant,for every 2" gain in barrel length. So according to your nonsensical theorum,my 24" barreled rifle will yield a 5gr greater case capacity than my 14" barreled XP? You should abort the sniffin' of the glue.

In a nutshell,you fail to comprehend the whole jist of ballistics and are relating Donald Duck-esque explanations of things that are apparently wayyyyy over your head.

I 'spose you think a 26" barreled 7-08AI,will Trump a 24" barreled 7mmRemmag in a Drag Race?

Pard,you can bullsheet the fans,but you can't bullsheet the players. There in lies your troubles,there are quite a few players on this field.......................

WT,
You might want to read this post on barrel lengths and velocity by Charlie Sisk. His findings might shed some light?
https://www.24hourcampfire.com/ubbt...&sb=5&o=&fpart=1

There is another experiment he did with other cartridges earlier, maybe I can dig it up, duh! MtnHtr

Hunter,

I often get long winded,instead of cuttin' to the chase. I shoulda cut to the chase and concisely related my thoughts,as to "snipers" muddled Post. Perhaps next time.

Anyhow,you touch upon much merit. There is a huge diversity in the affects of barrel length upon specific chamberings. "Overbore" and "expansion ratios" are the most often mentioned labels,geared towards specifying the causes.

Back to the crux of this Thread,the 7-08 is VERY barrel length "friendly". Meaning,it is not radically affected by subtle deviations. However,there are numerous offerings that do not share that attribute.

I know you know all of that and none of the above commentary is directed your way. I side with your thoughts and selections upon the matter,as they simply work(and well)....................

I can simply tell you what I have experienced over the last 7 years and almost 1500 rounds of ammo. I keep logs of all data from my shooting sessions. I know the velocity in MY factory barrel was 3000fps when I made it an ack. imp. That was recorded using a nosler 140 bt with 44.3grns of H-varget powder, bullet seated .010 off, winchester wlr primer. When I got the 26" barrel the load changed to 46 grns H-varget powder and velocity went to 3125fps. Then I tried the barnes xlc xbt. At first I shot patterns instead of groups until a friend suggested I seat the bullet .030 off instead of the reccomended .050. Velocity of my final load was 3185 fps with groups printing .5moa or less consistantly. My best was .435. So maybe powder amount jumped almost 2 grns. Excuse the @#!* out of me for being .5 grains off. What powder are you using? I have only tried the varget. If there is something that will kick my velocity up even more please tell me. I have tried the H-4895 but it slows my loads down. Although the groups tighten up a little. I do know the shorter barrel slows the velocity down. I worked up a load for a gunsmith that built a 08imp. with a 24" barrel for an NRA auction. The coated barnes has wound up being the best velocity producing bullet I have ever worked with and all I could get him was 3095fps from his shorter tube and still get a group of less than an inch. So just how far off base am I? Your xp shoots a 120 grn bullet. That bullet is shorter than the 140 allowing you more case capacity. So you should get a higher velocity from that short barrel. But we are talking 140 grn bullets here. I know your xp doesnt shoot them at 2750. I bet your 24" rifle pushes tthe 120 around a little over 3200. Try to get 3185 with a 140 grn bullet from it. Never happen. If it does you are getting some ungodly chamber pressures. So who's sniffin the glue here? The figure of 50 fps is a very general figure in loss or gain that vill vary from caliber to caliber load to load. But velocity and barrel length are directly proportional. Barrel length also affects accuracy. Some loads do better with long tubes and some with short tubes. I have a friend that built a 7-08 on a 700 action and outfitted it with a 24" Hart barrel. Accuracy sucked till they got the barrel down to 20". After that it shot like a dream. So every barrel to itself. Some do better being long and some short.

Let's source a little (pressure tested)data,courtesy Nosler #5.

7-08/140gr rifle data(test barrel is 26") page number 235. Top speed = 2922fps.

7-08/140gr pistol data(test barrel is 14") page number 557. Top speed = 2515fps.

Barrel length discrepency is a full foot of length (12"). Difference is 407fps. That 407fps velocity divided by the 12 inch barrel length difference,yields a factor of a whopping 33.91fps gain(on the average),per inch of barrel ength to the tested 26 inch.

One could only imagine the pitfalls of hitting the dreaded 27 inch cliff you mention(grin!).

My point is: you went to great lengths,in order to MISTAKENLY denounce thought processes of others,for applications that interest them. The difference in a couple of inches of 7-08 barrel length is less than 100fps on the average. Same goes the 280 or 7mmRemMag and even STW.

Point being,the gents that built those rifles knew that.

Second point being,a shorter/faster handling rifle offsets a mere 66fps velocity loss with it's handling properties and another bonus is the increase in barrel rigidity(though slight and myself being a proponent of slightly contoured tubes).

Eeking max light contoured barrel accuracy potential,is a subject deserving of a Thread of it's own. But I'll hit the high spots and mention that a quality barrel that is properly stress relieved,coupled with a rigid stock(McMillan or bust) and proper bedding will dazzle on the average.

Nowwww looking further down the line,I could comment upon other higher intensity 7mm's I've enjoyed. That from 284Win,280,280AI,7mmRemmag,to 7STW. Rest assured,there was a little barrel length deviation amongst thoseranks too.............

wts: welcome to the campfire.

While I'm sure nobody is doubting your velocities, you may simply be experiencing the "fast bbl/slow bbl" effect. Given equal pressures a 2" increase or decrease in the SAME BARREL, would never account for the velocity increase that you cite.

Interestingly, the 284 Win with more capacity than your AI rarely reaches 140/3000 in pressure tested loads. Having studied small case 7mm ballistics some myself, I might question your pressures. Varget is a faster powder than one would normally expect to deliver that kind of velocity in that small a case.

I'm sure that you get the velocities that you state, but the fact that your rifle exhibits no obvious pressure signs may not be assurance that your load is "safe" You might peruse the article entitled "Pressure Guessing" by John Barnsness (Handloader 10-02) The anecdote in the first two paragraphs might be worth noting.

JimF

Jim,

That is one door I left purposely wide open and I'm glad you closed it!

It has been my experience in the 7-08,that the personality of an individual barrel,weighs more heavily than specific length. Meaning that a "fast" 22 inch tube,will easily eclipse the performance of a "slow",24 inch tube.

I'm of the opinion that when splitting hairs that finely,the bore's internal properties and throating arrangement,weigh more heqavily than two inches of barrel length,in this chambering

As was mentioned prior. This Board is steeped in players..............(grin)

Stick, Jim
I have a Rem. 700 in 7-08. It is a 700 ADL sititng in a Remington Tupperware stock. It has a 20" factory barrel.

I shoot 42.5 gr. of IMR 4064, Fed. 210 primers, Nosler 120 BT, .080" off the lands.

I "CONSISTANTLY" shoot cloverleaf groups at 100 yards.
At 150 yards my groups open up ever so slightly.
I shoot these same "dime" size groups from a clean or fould bore.
In all honesty my first shot from a squeaky clean bore is approx. off 1/4" at 100 yards. My longest shot ever on game has been approx. 135 yards.

After reading many posts over the years I'm beginng to be unsatisfied with the "dime" size groups my rifle "consistantly" shoots.

After all: I dont know what the velocity is. I dont have an ackley. The barrel could be longer. The stock isnt a Mc....( this may be taking it too far). And dang my bullets arent blue.

Now that I'm learning what barrel length, contour, bullet, powder, and chambering I SHOULD be using. I'm thinking I might need to change.

<img src="/ubbthreads/images/graemlins/wink.gif" alt="" />GB

WT,
Keep in mind when you move your bullet closer to the lands in a given load, pressures rise. Your slight increase in velocity( your 26"bbl)came when you moved your Barnes 140 XLC from .050" to .030", this is normal when seating your bullets closer to the lands and not just from the powder increase if I read your post correctly. Like Stick posted you really can't compare two different barrels in regards to velocity and powder charges. The differences in chamber dimensions, throats and bore dia. leave too many doors open to make a valid comparision. MtnHtr

I think Jim F and big stick have hit upon a very interesting point. Every barrel seems to be its own animal. I have a 338-06 imp. Charlie Sisk built me that seems to achieve very high velocity out of a fairly reasonable charge of IMR 4350. I don�t have the loads in front of me, as I am half way around the world, but if I recall correctly, the load is 56 grains of IMR 4350 (not too hot for a 338-06 imp.) behind a 225 grain partition. The velocity out of my 24� barrel was something like 2,730 fps. Do you recall Charlie? Anyway, the point being, many reloading manuals show this load to be about 2,600 fps. This is a big difference. Maybe this particular barrel builds higher pressures then other barrels? Therefore, this gun realizes a higher velocity for a given charge of powder then other guns? Who knows, I am no expert (that is why I read these threads), but that is about the only thing I can attribute it to. Maybe WS is seeing the same thing in his barrel? If so, his pressures could be off the charts, as 3,185 fps is cookin for 7-08!!

One other question, how does a longer barrel affect the amount of power one can stuff into a case?

Ted

tevans, haven't seen you around for a while. How are things?

tevans:

The point that a couple of posters were trying to make is that barrel length has zero effect on case capacity. The length of the throat may affect "useful" capacity somewhat. A case with the bullet seated to say .100 longer c.o.l. will have more capacity below the base of the bullet. This extra capacity is often useful in small cases when loaded with fairly slow powders. (the 7-08 is an example).

Occasionally on this board, we will see some claims of a certain velocity in a certain case and be concerned. Not so much because we think the shooter is B.S.ing but out of concern for a fellow shooter. It's easy to elevate pressures beyond safe levels in order to reach a certain goal that you "want" your pet project to achieve.

JimF

I have been well. Unfortunately, I have been traveling and working. Therefore, I haven�t had much time to check the list lately. I am still living in England, the weather still sucks, the beer is still warm and the Brits still don�t go to the dentist, other then that life is the same:-)

I hope to move back to Colorado in the fall sometime. I sure miss the place. Not to mention, I can�t wait to get back to the States so I can work up some new loads and start shooting again. Over here I have to live vicariously through the guys on the list, as it is virtually impossible to own a rifle here in the UK. If you think gun laws are restrictive in the US����you wouldn�t believe what it is like here. A lot of the shooters in the UK think guns and shooting sports will be extinct within 20 years. That is grim!!

Ted

GB,

You oughtta know that I'd be amongst the last cuss a Factory rifle,especially a Remington and in 7-08!

Many Factory rifles,shoot on what borders the incredible. I've seen my share of them and in many different configurations. Those are the rifles I like to "upgrade",because they are a known quantity.

I've happily punched out a number of rifles like that,to Improved chamberings of the parent cartridge or went even further. Case in point: a Rem 700 S/S BDL in 7-08,that shot in the mid to high .3's with 130MK's and the straight 16X Leupold on top of it,while wearing it's tupperware stock. I punched it to 284Win and put it in a swirled McMillan Classic pattern and am in LOVE with the damn thing now. A stock swap can do wonders to fit/feel/and felt recoil,before you even get to mentioning accuracy properties. Point being,I'll happily upgrade a great shootin' Factory Iron.

I think a 7-08 with a 20" tube is a wonderfully effective animal. It would take more than that to keep me at home(grin)....................

GB,

One (1) question and one (1) comment:

Is your Model 700 ADL in its original "factory" configuration or was it modified? I thought that recent production Models 700 ADL came with 22" or 24" barrels, unless they were 20" youth guns.

If you can shoot sub 1" groups on a regular basis with a "factory stock" rifle, I wouldn't change a thing or it might shoot bigger groups!

Sincerely,

Bearrr264

WTS,

I will state for the record that I don't know squat about either the 7mm-08, or the AI version, as I am the antithesist of a 7mm-08 fan. However, I have looked at the Jarrett site, specifically their velocity claims for the 7mm-08AI, and I think that they are either very optimistic or the loads being cited are loaded above and beyond what I would consider a reasonable degree of safety.

Sincerely,

Bearrr264

PS What makes a 27" barrel "optimal" for achieving maximum velocity in the 7mm-08?