Home Forums Hunting & Shooting Custom Rifles & Wildcats Bob Jourdan and his perspictive of the AI's

One of my very favorite gun writers and one of the finest of gentlemen, gives his personal outlook on the

Ackley Improved cartridges.



http://www.precisionshooting.com/psm_2003_07_frame.html

Good article. He sure is making me look forward to my .250 AI that should be here in about two weeks!

John

Interesting article and it provides at least a basis for comparison between the various AI's. Clearly, the sharply tapered cases (250 Sav.) show the greatest potential gains vs. say the (.308 based) cases.

It surprises me somewhat that BJ is not more clear on the pressure differences between Ackley's data and some of the factory figures he (Jourdan) quotes. Given human nature, when some shooters get the hots to "improve" something, they tend to look at the highest velocities they can find and assume that their project will realize those gains. Unfortunately, they start stuffing powder in the case and chronying loads until they reach those figures. Often, those loads are too hot.

"She ain't blowed up yet" is not a sufficient indication of safe pressure.

Shooters getting all fired up over Ackleyfying something would be wise to include in their research, John Barnsnesses' recent article in Handloader titled "Pressure Guessing" As most modern (pressure tested) data confirms, the 4-1 rule of case capacity gains vs. velocity increases is nearly inviolate. In many instances, standard cases when loaded to safe maximums will shrink the gap between themselves and an improved cartridge pretty significantly (assuming the AI is loaded to the same pressure level).

This is not intended to denigrate Jourdan as a writer. I am simply of the opinion that his article is incomplete. An inexperienced shooter could possibly get the wrong idea about the potential gains from AI's if he were to take this at face value. In Jourdans defense, while some of the velocity gains that he quotes are probably not realistic, the article does give an idea of the relative merits of several of the AI cartridges.

JimF

JimF,

You list some good points pertaining to Ackley Improved cartridges. While some people only search for velocity improvements there are other attributes to the improved cartridge. To me one of the more outstanding results from the improved cartridge is almost never having to trim the cases. Another is an item I CAN'T PROVE but I believe you can reduce the ES (extreme spread) on velocities with the Ackley Improved design. Like I said, I can't prove it but I think it is there as compared to the factory cartridge.

I am just about finished with my long range varminter chambered for the 6.5/08 Ackley Improved. In BJ's list of cartridges this one is at the bottom on velocity gain. I opted for the AI version for the reasons stated above. Only time and a fair amount of shooting over a chronograph will tell me if I have achieved my goals.........we shall see.

Your critique was well thought out and presented fairly--I thank you for jumping in with your thoughts on the Ackley design.

Ol' John

John:

I agree with your reasoning completely. In fact my next varminter will probably be a 22-250 AI (slow twist) for the exact reasons that you stated. I don't care much about the velocity increase (if any) but I'm getting tired of trimming cases for my 22-250 encore.


JimF

I have owned a couple of 250AIs and never could get close to gaining 500 +/- fps with a safe load. Maybe you could do it with a full case of Bullseye, 2400, or nitoglycerine, but not with any generally accepted powder that I could find.

On pages 333 through 335 of Volume I, POA claims the following:

250/3000 Savage

100 grain bullet with 39 grains of 4350 will go 2750
(To compare, Hornady claims that a max load of 37.9 grains of IMR 4350 will go 2800 with a 100 grain bullet on page 130 of their 3rd Edition)

250/3000 Improved (Ackley)

100 grain bullet with 43 grains of 4350 will go 3276

Do you seriously believe that you can get an additional 526 fps by burning 4 additional grains of the same powder in a larger case? I don't. I've owned and loaded for the 250-3000AI and I personally think that it runs a poor 4th in the race of short action 25s behind the 25-284, 257 Roberts, and 25 Souper.

POA knew that velocity sold rechambering work and that very few people would be able to prove or disprove his claims due to the lack of affordable chronograph equipement in those days. I have AIs, but I have begun to believe that much of what POA claimed was annalagous to the HCA story of the Emporer's New Clothes, in that they were wonderful because everyone wanted them to be wonderful.

Jeff

I liked the article too. I do disagree with his 6% rule. If cases really will last 15-20 firings (didn't in my 375 Ack, but I was new at "acking" then), then a 100 fps increase with double the case life would be worth it. Maybe even just double the case life..........................



Blaine

I'm on a batch of RP 280 AI brass that is 22+ firings (got tired of keeping track). I anneal the necks every 5 firings. Case trimming - what's that? An Ackley is well worth the effort for this reason alone IMHO. Plus, one must admit that the 40 degree shoulder looks pretty cool <img src="/ubbthreads/images/graemlins/tongue.gif" alt="" />

280_ACKLEY

.260 RemGuy,

I think I probably have to agree with you when you put the .250 AI gains in terms of 500 fps increase. Probably somewhat optimistic. However, given that the .250 AI shows a 15 to 17% increase in powder capacity, it is still going to show more gain than most of the other Ackley cartridges. Pressure remaining equal, the Ackleys that increase the most in volume are going to show the greatest increase in velocity, right? If we accept this as being true, then realistically, according to MD, we can expect about a 4% increase in velocity for the .250 AI over the standard chambering. That should put a 100 gr bullet out at about 2900, if we keep the pressures the same. But wait..... The industry standard pressure for .250 Savage is 45,000 CUP (Speer #12). If we boost the pressure to 52 or 54,000 CUP (25/06 & .270 Win pressures), we gain quite a bit more (I couldn't find the industry pressure for .250 Savage in PSI). Some guys have quoted me 3200+ with a 100 gr bullet from the .250 AI. I expect 3100 will be reasonable. Of course, load the standard .250 Savage up to 52,000 CUP, and it is probably going to give 3000 or so with the 100 gr bullet. My Sierra manual shows several 100 gr bullet loads at 3000, and Hodgon shows one load at 3100. Add 4% to 3100, and the .250 AI might give 3214! Hmmm. Not far from some of the quoted figures. But..... even if the AI version doesn't turn out to be a ballistic miracle, the standard version sure doesn't look as cool <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />!

John

I read the first part of Jourdans article, whoever he is, and he regurgitates the same old myths about improved chambers.

I view them as nothing but larger cartridges than orginal ones that are loaded to higher pressures. I have seen no improvement in case life, stretching or relative velocity. But then I have a chronograph and Kilbourn and Ackely did not.

There are two cartridges however that are even worse for reloading than the so called improved or fire formed ones and they are the 300 HH and the 458 Win. They could be "improved" by an adequate shoulder. The others are a past time or money maker for gunsmiths.

Improved chambers are good for getting thru the winter however.

I don't agree with his arbitrary 6% rule, either, but much less improvement than that requires the Ackley owner to have more in mind than just velocity when rechambering. That's a good thing. I've never had to trim Ackley Improved cases. I believe the Ackley chamber to be easier on barrel throats. If someone can get the same or better velocities as the standard cartridge, but do it in a shorter, handier barrel length with the Ackley chambering, he's gained a more useful hunting tool. And it does make for a sexier looking cartridge, doesn't it?

A more important consideration, though, is whether or not one is having a barrel rechambered to the Ackley configuration or building a rifle from scratch for an Ackley cartridge. Rechambering requires the owner to expend precious funds, only to have to reuse the same factory barrel, which may not be a good thing. The owner also winds up with an extra set of dies. However, if someone is having a rifle built, it really doesn't matter what chambering is chosen. The barrel is chambered, headspaced, and installed only once. Money is spent on only one set of dies. And if the owner is like me, he doesn't get rid of rifles once he acquires them, and has something not everybody else on the block has (always good for deer camp conversation).