I am kinda new to all of this stuff and I have a question about AI cartidges. What exactly is and AI cartridge? I hear stuff like "the ackley treatment" etc. and I would just like to know what you guys are talking about.
Thanks

Parker O. Ackley, experamenter and wildcatter.
Ackley Improvement: Minimise the body taper and increase the shoulder angle to increase the available powder room (more room=more powder=more velocity at the same pressure level). Some cartridges are better suited for "improvment" than others, as there is a 4:1 relationship between increased capacity and increased velocity (at the same pressure level) IE one with a large taper to the body (.030/inch) and a shallow shoulder angle (say 8deg) will show a much larger gain than one with a fairly streight taper (.004/inch) and a 30deg shoulder). One of the Ackley signature features is that factory ammo could be safely fired in his chambers.

PO Ackley wasnt the only guy doing this, Mashburn, Kilburn (the 22 K-Hornet is one of his), Roy Weatherby, Rocky Gibbs are just some of the others that were doing similar things.

A lot of yesterdays ammo designs need/needed help, but today many of the factory offerings duplicate what they did that the gains are much smaller now.

And AI cases with less body taper don't grow in length as fast as the parent case; you won't have to trim as often. And that's why when I had two rifles re-barreled I decided the 223Rem AI and 338-06 AI would be just what the doctor ordered. And my gunsmith didn't charge any more for the chambering than with the parent reamer.

Talked to a real good custom rifle maker and he told me the AI 260 was a real winner. The gain in velocity was in the 400 FPS range. Thinking about having my present .260 rebedded ina real good stock and go with the AI conversion.

I am sold on them, even if the velocity increase is minimal in the cartridge used. I am very happy with the positive headspacing the 40* shoulder gives and the lessened case growth and primer pocket loosening.

I have the 6.5x55AI, 280AI, and 6.5-06AI.

quote:

Talked to a real good custom rifle maker and he told me the AI 260 was a real winner. The gain in velocity was in the 400 FPS range.

A four hundred fps increase is absurd. The gunsmith is not even a good talker as it's impossible.

The AI line is just a copy of what Kilbourn started and it's no real improvment at all. It's fun however so go at it. I have mine and wish that I had standard cartridges.

Like he said to the guy about to climb a tree to catch a racoon bare handed "I told you not to do it".

"A four hundred fps increase is absurd. The gunsmith is not even a good talker as it's impossible"

Your statement is absurd. You can realize 300-400 fps with several of Ackley's creations.

Steve.
since no one has explained this part yet I will do so.
You take a standard chambering , say a .257 Roberts and have the chamber reformed to .257 R AI,
You then shoot a standard cartridge in the chamber and and the brass expands to the shape of the AI chamber. the reduced body taper and sharper shoulder adds powder space. although in some rifles it can cause feeding problems. I would expect a 100 to 150 Fps gain.
...tj3006

I've built AI's ,Gibbs and my own wildcats with more capacity increases than the gibbs. Using a pressure guage on several. I know there are people that are getting thoses increases in velocity but, only because they are using a much higher pressure. Take a case that is capably of 2800 FPS. A 400FPS increase is 14.3%. The norm is .25% velocity increase for each 1% increase in powder. As the cases get bigger that becomes even less. So to get that velocity increase you need a 57% increase in powder.

Take a look at the difference in powder capacity between the 7x57 and 7MMWBY it is right at 58% take .25% (14.5%) If you assume you can get 2800 from the 7x57 then you should get an additional 406fps or 3200. Yes I know that most books show the 7wby at a little more than 400 above the 7X57 but the WBY is loaded to a much higher pressure.

People do load their AIs to higher velocities because their cases are formed to the chamber, they have less taper all of which allows then to go to higher pressure without "seeing" signs of problems. Strain guages don't lie. There is no free lunch.

The ratio of velocity increase to powder is around 25% when both are loaded to the same pressures. Take your loading books and programs and compare it yourself.

What they are is a theoretical waste of time.........

AD

400 fps increase from 260 to 260 AI would definately fall into the absurd category........

quote:

Originally posted by steve4102:
I am kinda new to all of this stuff and I have a question about AI cartidges. What exactly is and AI cartridge? I hear stuff like "the ackley treatment" etc. and I would just like to know what you guys are talking about.
Thanks

One more little detail: To qualify as an "Improved" chamber, the gun must chamber and fire factory original ammo too. Just wanted to clarify it is not an option. Mr. Ackley coined the phrase and that's his rule.

When you push the shoulder forward like Gibbs or make any other change that precludes safely firing factory ammo, then you have a pure wildcat.

weatherby is a waste of time, so is gibbs, so is the K- whatever's also. Anyone who uses the radiused shoulder or a 30-40* shoulder is benefitting from Ackleys theories as well as his collegues. setting aside any worn out and steeped in OPINION statements regarding velocity, the positive headspacing from the shoulder angle alone is an "improvement" for me. But then again, I don't even own a rifle that shoots 1MOA, those get sold off to someone who has opinions about case designs and too much time on their hands. My Ackelys, after rechambering, are more accurate than their parents were. I won't prove to the peanut gallery that I have only opinion,..I will simply say that IN MY EXPERIENCE the ackley outperforms it's parent. The sharp shoulder also allows for more firings at higher pressures due to reduced growth at the neck and expansion ring. That alone is my idea of an improvement. If it can handle higher pressures safely, then that is indeed an improvement in my world. My 6.5x55AI is running a 140gr pill at 3000fps and is maintaining primer pockets for quite a while. Try that with the original. My 6.5-06AI did not crap out primer pockets until it hit 3200fps with 140gr pills (both 26" tubes) and that was after a few previous firings, not the first firing.

YMMV,..anyone needing to rid themsleves of their terrible and far too involved ackely chambered tubes,...I'll pay the shipping to me and maybe throw you some brass for your non-ackley projects,..cause I am a friend of the people and always willing to help.

quote:

Originally posted by Jim White:
"A four hundred fps increase is absurd. The gunsmith is not even a good talker as it's impossible"

Your statement is absurd. You can realize 300-400 fps with several of Ackley's creations.

His statement may be absurd, but I'd like to see a .260 AI (or any other improved version of the .260) get 400 fps more than the standard round from an identical barrel - or better yet, the same barrel, before & after......

Now, we are agreed that there'll be no blowing of primers!! Bullet and primers to be the same.

BTW, exactly which AI round(s) will get 400 FPS more than the standard round??? Just curious.

El D, none! I have a .260ai & I would think I am getting maybe 75fps greater vel. I do like the fact that the cases stretch less & it's a very cool looking round. Is it better than a .260rem. probably not, but I was having a new bbl. put on this rifle anyway, so cost was identical. Cases are the same, you can load them on std. .260rem neck dies. If I had to I could use factory .260rem ammo, so I see no real down side to AI rounds. If you like them get one, if not don't, but don't expect hyper vel. gains either.

I have a 257 AI, a 25-06 AI, a 280 AI, and a 30-06 AI. The 257 AI and 280 AI are real improvements, especially the 257 AI, which is essentially a 25-06 in performance. The 30-06 AI is only mildly improved, getting ~75 fps more than the std 06 when everything else is equal. The 25-06 AI is well over bore, very hard on barrels, and not much of an improvement over the 257 AI or 25-06. I don't recommend the 25-06 AI, neither did Ackley. In my opinion, the 280 AI is about perfect bore (given current powders) for the 7 mm caliber.

All have been very accurate and neck lengthening is stopped by the sharp shoulders. I find that all primer pockets begin to loosen when you exceed 65,000 PSI, no matter the case design.

If you had a gun chambered with a 06 bolt, and you wanted to rebarrel to a more powerful cartridge (but keep you bolt and action), your best best would be either 30-06 AI or 280 AI - they are twins in performance. If you liked 25 caliber, going with 25-06 or 257 AI would yield equal results.

The cases that benefit from minimizing body taper are naturally going to be the ones with a lot of it. The 260 is already somewhat "improved", very little body taper to begin with. I wouldnt bother Ackleyizing anything that was parented from the 308.

Ive got a 257 AI and it is about as good as improved gets, it doesnt see a 400 fs gain on its best day! A 260 gaining that much IS absurd.. That 'smith is either full of shit or is scaming you.

I would advise anyone considering going the improved route to be very selective about what they do it to. It has been done to nearly every chambering you can imagine and only a handfull of them realize enough gain to actually be called an improvment and to justify the extra cost of improved dies and the time involved in fireforming. There are other tangible benefits as well, but for a measley 50 fs gain, MHO is dont bother. For instance going from a 35 Whelen to an AI is a waste of time. Better to blow it out to a Brown Whelen or a Gibbs and see some real gains since you need to spend extra on dies and fireform anyway. Its not like seating the bullets to the lands is a major task.

And by the way, an AI chambering still qualifies as a wildcat. Wether or not wildcatting itself is a waste of time is highly subjective, but there certianly isnt the need for it today that there may have been in the past.

I have AI rifles, but do as I say, not as I do, stick with the non AI, and save some time.

As stated above, best gains come from large tapered, shallow shouldered, long necked cartridges, most of which are much older designs than most people use today. The 38-56, for example, gains some 41% in below neck capacity, the 348Win about 17% the 30-30 about 11.5% and the 256Bob about 7% vs the 30-06 which only gains about 1.5% (and the 308 baised cases will be even less than that due to the straighter body/sharper shoulder design of the origional).
What accounts for a lot of the claimed gains is that the owners "crank up" the pressure levels their operating at to maximize the velocity gain.

I get about 3 to 4 grs more powder (4-5%) in the 30-06 AI vs the standard 30-06.

it aint always about velocity. Case life and less changes in it's shape and hardness make a difference as well. The ackley cases last longer when run at similar pressures. If you use Lapua, Norma, RWS, DWM, etc brass, then the savings in brass life is also an "improvement" in terms of your wallet.

There are some cases that even in Parker's own admission don't benefit from the conversion, such as the 25-06 which is already overbore. So, buyer beware.

AND, to clarify the fireforming myth, I run the load ladder when fireforming and it runs consistent with the finished product. Therfore, their is not any barrel life loss,..but again YMMV.

Look at the 6.5x284 winning benchrest matches right now,..it has a straight body and a 40* shoulder.

Another but weak reason to use an AI chambering.
I have two 30-06's. I AI'd one so that I can tell which rifle the brass was shot in. But I am weird and like to use the brass in only one rifle. Thre isn't much reason to AI unless you are trying to get max performance from some old rifle like a 30-30. The 30-30 AI gives a little bit more performance since the case has less taper and clings to the chamber better allowing a bit more pressure than a standard 30-30. With today's selection of cartidges that fill almost very niche their isn't much reason left to AI a round.

Just as a note, I am on my 10th firing w/ the batch of .260ai brass I have. Half is .260RP the other half is .243WW necked up. I've trimmed them once. There is no real downside for me as I use 2-3 new cases to foul the bbl. before shooting my AI handloads for group. WOuld I do it again, maybe not, but I do enjoy the little .260ai.

I only see one reason not to:

"because I don't want to have to fireform brass and waste my barrel life"

I don't mind doing so because I work my load ladder at the same time. They can be used to run higher pressures while lasting the same or longer than their shallow shouldered kin. Ifin you choose match cases and take the time to match prep and then run it all through a match tube, then the AI could be just what you need. Ifin you run around the woods or shoot of your rearview mirror, then it's likely you will never be able to justify the conversion. However, that doesn't negate it's advantages when applied correctly. For match chambers and long range work,..I have found every AI I ever loaded for to be a great performer with great case life and an uncanny propensity for accuracy that I have come to expect before ever firing the first round.

Explain to me the .004" crush fit that Ackley used. As I understand it to be a properly chambered AI needs the barrel to be set back, correct?

Two years ago I passed on a 257AI, a pre-'64 model 70, at a gun show because I couldn't tell if the barrel had been set back or not. I had the guy talked down to $800ish, but I passed anyway. Did I make a mistake?

Here is an obsrvation on the AIs
As stated in this thread, the bigest improvment is on .257 R AI and 280-AI.
And I have herd this before in other places. I have no AIs in my collection at this time, so mabye i don't know what i am talking about, but it seems to me that the standard .257 and the 280 are downloaded from the factory. Remember the Roberts has been built on many old 93 and 95 mausers. not suitable for modern preasure levals. and the 280 was designed for the Remington 740 auto.
and the same aplies there. Not saying AIs are a bad thing or don't work just that mabye the 2 cartridges I am naming are just underloaded from thr factory and in most loading manuals.
Then when a guy starts working up loads for his AI he goes to much higher preasures than he would with a standard chamber ? ...tj3006

I have seen two guys that got 257 RAI, that were not up to the task, and would have been far better off with a 257 Roberts.

quote:

Originally posted by fredj338:
... WOuld I do it again, maybe not, but I do enjoy the little .260ai.

Hey Fred, Any chance you measured the Velocity prior to going to the AI, or did you just chamber it that way to start with?

What is your barrel length and what kind of Velocities with the bullets you are using?

I realize it is a "Sample of 1", but it might shed some light on the 400fps increase from 260Rem to 260AI.
---

Hey Blob1, How `bout asking that GunSmith once more about the conversion? I can see a 400fps increase possibly being done with a 257Rob or 7x57. But, the 260Rem appears to be pretty close to State-of-the-Art as it comes from the factory, so it just seems there is "less potential" for increasing the Velocity to such a significant degree.

Perhaps he was thinking 257Rob or 7x57 and just said 260Rem by mistake. Easy to do the older we get.

quote:

Originally posted by Thomas Jones:
Here is an obsrvation on the AIs
As stated in this thread, the bigest improvment is on .257 R AI and 280-AI.
And I have herd this before in other places. I have no AIs in my collection at this time, so mabye i don't know what i am talking about, but it seems to me that the standard .257 and the 280 are downloaded from the factory. Remember the Roberts has been built on many old 93 and 95 mausers. not suitable for modern preasure levals. and the 280 was designed for the Remington 740 auto.
and the same aplies there. Not saying AIs are a bad thing or don't work just that mabye the 2 cartridges I am naming are just underloaded from thr factory and in most loading manuals.
Then when a guy starts working up loads for his AI he goes to much higher preasures than he would with a standard chamber ? ...tj3006

You can buy +P 257 R loads over the counter that run at pressures designed for stronger actions. Im not goiing to try to explain why, but I still get considerably better performance than the +P loads from my AI with a 24" tube. It is the ballistic equivalent of a 25-06.

HotCore, the rifle was originally a .308 so I wanted something a bit better for varminting & still be able to do good target work out to 600+. So this was a new chambereing, 27" PacNor SS match, Sendero profile (med. heavy). Typical vel.
48gr IMR7828sssc-142grSMK = 2825fps
48.5gr RL19-123grLapua = 3100fps
43gr H4350-139grLapua = 2830fps
46.8gr H4350-123grLapua = 3075fps
44gr VV150-85gr Sierra = 3415fps
So as you can see, you might get 100fps from some loads but I doubt it. What I do get is .260rem vel. w/ a bit less pressure & exc. case life. I'm happy w/ it & fireforming is no big deal The original 30 cases were from mountng the scope & breaking in the bbl. I fire 3 new cases everytime out to foul the bbl. & just keep using the original cases.

Hey Fred, Thanks for the info. It seems to be about what everyone expected when you figure in the additional barrel length.

Did you have difficulty locating a Gun Case for it? (27" barrel and all)

quote:

Originally posted by fredj338:
So as you can see, you might get 100fps from some loads but I doubt it. What I do get is .260rem vel. w/ a bit less pressure & exc. case life. ...

Obviously a worth while project when viewed from that perspective. Probably get a very long barrel life as well.

Best of luck to you.

Just curious, why is it no one ever talks about a 270 AI? Is it because the 270 is perfect already and there's nothing to be gained?

I have been shootin a 243AI 26" 1-10 douglas barrel. Ackley says I should get 3700f/s with 44grs Imr 4064. 75gr bullets.
47th reloading handbook max load for a 243 at 3460f/s 40.5gr of imr4064
I am getting 3316f/s with 41.6 grs imr4064
10 rounds has a S.D. of 4 f/s.
AGG (5/5 shot groups) at 100yds is .317"
dont think i can get much better.

257 Roberts is one of the best cartridges to AI. You gain some capacity, and since your AI brass won't fit a standard chamber you can up the pressure to 60K psi instead of 47K psi fairly safely (but only if YOUR rifle can handle the pressure). This can give you 400 fps increase, but most of the extra velocity is from the higher pressure, not the slightly larger case.
Same is true of a few other cartridges like the 8x57 that are loaded to lower pressure levels than a modern bolt action can handle - going to the AI chamber means other rifles that may not be very strong can't fire your high pressure AI ammo.

quote:

Originally posted by woods:
Just curious, why is it no one ever talks about a 270 AI? Is it because the 270 is perfect already and there's nothing to be gained?

I expect that the answer to that is that another aspect of cartridges that benefit from the sharper shoulder/minimized taper changes are that it is also most effective on cases that are somewhat underbore, such as the 30-30. The 270 already has a generous powder capacity for that bore and as such probably wouldnt yeild much gain. YMMV.