243 ai

atom

Well-Known Member
Hi a mate of mine just brought his first 243 looking at it i noticed it has 243ai stamped on it he did not realise it was not standard it shoots fine with standard 243 bullets will it create any probs and is it legal on his ticket cheers the atom
 
Legal on his ticket and it will not cause any issues. He will notice however, the cases 'blowing out' once fired to the dimensions of the Ackley chambering.

When I used factory ammunition to fire-form cases for my .243AI, I cannot say that the accuracy was not what I would have expected from standard .243 in an AI chember . Does he not home-load?
 
no he does not home load so really he could sell his spent cases for other reloaders
 
If chambered correctly a 243 ackley chamber has slightly less headspace than a standard 243 so factory ammo may be tight in the chamber, this difference in headspace can, with factory loadings of heavier bullets, lead to the bullet touching the rifling leading to an over pressure situation.
Can't use factory ammo heavier than 80 grains in mine without heavy pressure signs
 
If chambered correctly a 243 ackley chamber has slightly less headspace than a standard 243 so factory ammo may be tight in the chamber, this difference in headspace can, with factory loadings of heavier bullets, lead to the bullet touching the rifling leading to an over pressure situation.
Can't use factory ammo heavier than 80 grains in mine without heavy pressure signs

can you explain this, I am confused. not being an arse by the way, just started reloading myself so still learning
I thought head space was the dimension from shoulder to bolt face.
doesnt the AI have a longer shoulder to bolt face than stock?
 
A correctly chambered Ackley chamber will accept factory rounds. You're right, the headspace datun point is different, but the results are the same. THe unfortunate part about "custom" guns in Ackley chamberings is that there is little standardization. If a gunsmith uses a thrice-sharpened reamer, you can get problems with the most cautious handloads. Ackley used seat bullets so that they firmly contacted the rifling, pushing the rim back against the boltface and in essence, supporting the case on both ends during the fire-forming process. Some shooters using 30-06 IMP (the last remaining of my Ackley chambered guns) used to pull service bullets from Lake City Match ammo (when it was cheap) and reseat them to hit the rifling hard, firing them with the original charge in place. It worked nicely.~Muir
 
slightly off topic but I have never really understood why all cartridges are not ideally held in place between bolt face and shoulder, I can see why factory ammo is not, as chamber/headspace size varies but for the home loader why do they full resize and bump shoulders back (assuming fire formed same rifle etc)? (something I was disappointed not to learn about having read Lee's volume 2.)

i get the 243 AI spec but is it not designed to reduce pressure for max loads rather than give you more charge space?
 
No. Ackley cases do not allow lower pressures, just more case capacity. And there's the buggerboo of Ackley cases. If you are shooting a 22-250 operating at 55K maximum pressures, and then increase the case capacity, the pressures and velocity will most likely drop if you have kept all the variables the same. So you add more powder to get back to maximum operating pressures. What have you gained? Nothing. If the pressures are the same then the velocity will be the same. You just used more powder to get there. Based on what I know of Ackley in his later years, I think he would be amused as to how shooters view his Improved chambers.~Muir
 
No. Ackley cases do not allow lower pressures, just more case capacity. And there's the buggerboo of Ackley cases. If you are shooting a 22-250 operating at 55K maximum pressures, and then increase the case capacity, the pressures and velocity will most likely drop if you have kept all the variables the same. So you add more powder to get back to maximum operating pressures. What have you gained? Nothing. If the pressures are the same then the velocity will be the same. You just used more powder to get there. Based on what I know of Ackley in his later years, I think he would be amused as to how shooters view his Improved chambers.~Muir

Muir, I have only ever used one Ackley chambering, in 243. For me the obvious advantage was no case trimming as the brass did not 'flow' as much, given I assume the case shoulder angle. I have read your posts on the Ackley chamber with interest over the last year. Are we to believe then, that the only real advantage of this concept is the reduced case prep required? It has always been suggested that the AI case improved 'burn' of the powder and was therefore more efficient so perhaps not having to use more powder to gain the same pressure. Or if taking a case in standard form that was at maximum powder weight but not pressure, thereby allowing greater capacity by increasing volume of case=more powder= greater velocity. I am simplifying obviously but take some of my comments from a custom rifle builder I know and avid developer of chamberings including some of his own.

I realise you knew Ackley personally and would be interested to hear what his principle reasons were in developing his concept, or for that matter your own thoughts.

Apologies to the original poster if this is seen as a bit of hi-jacking but it is still subject related and may be of interest to your friend.
 
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JR: I knew Ackley to the extent that we corresponded regularly for a little over a year. It began with me disagreeing with him in a gunsmithing column in "Shooting Times" (US) magazine about forming .256 Winchester Magnum from 357 Magnum cases. He ended up writing to me personally and so the dialogue began. I later attended classes at Trinidad State College where he taught and did much of his research, tho he had passed away by then.

Within our correspondence, we discussed ballistics and eventually the Ackley shoulder. He believed that it promoted a more efficient burn but that is something that, with the exception of certain combinations of case shape and powder, has been largely disproved at last look. One of the reasons to look into the Improved shoulder was the availability of cheapo, slow burning military surplus powders. 4831 was sold from barrels in hardware stores at one time, and it was cheap. Guys were loading it in .22 Hornet and 222 Remington. There were many cartridges in which a case full of 4831 just didn't generate any pressures and low velocity. It was these cases that Ackley's shoulder benefited the most. A person with a bolt action 30-30 of good quality had two problems: the long tapered case that tended to blow the column of slow to medium slow powder down tube before useable pressures could be obtained (one of those special combinations I spoke of) and the small case capacity for these powders. The Ackley chambering solved these, or improved these to a great extent. Thirty-aught-six shooters could stoke their 06's a little more, even.

What Ackley thought a waste of time for practical applications was improving a high-intensity cartridge. A factory round developing maximum allowable pressures (and they are built to do so, trust me) can hardly be improved on by adding case capacity. If one sticks to the approved pressure limits, then you pour more powder into the Ackley chamber until you reach that pressure again. If the bullet and barrel length are the same, you should see little difference in velocity and of course, we already mentioned that the pressure was the same. Unless you have existing barrels rechambered with an Ackley chamber, it's impossible to realize unless you have a pressure test gun. Here in the US gunsmiths who specialize in rebarreling gently push customers towards longer barrels. That will give you velocity increases od substance. A buddy of mine just got a 243 AI with a 30 inch barrel. You bet! More speed!!

I believe that Ackley did much of his experimentation because he could. He had marvelous equipment and the freedom to use it. One of his students, Deward Finley of Raton, NM attested to that. I apprenticed with Deward who was a fine barrel man and an admirer of Ackley. One thing Deward told me was that, tho Ackley's books were popular, the real "skinny" on Ackley's chambers was written by Ackley for the Lyman Gunsite Company in their #43 (IIRC) reloading manual where he talks about the kind of cartridges that should be "Improved" and those which should be left alone. My coments above about hi-intensity cartridges mirror what he wrote there.

That anyone's "Improved" chambered rifle is a fine gun and a serious shooter, I have no doubts. My 220 AI Swift was a screaming tack driver and I have often wished for it back. That you get better case life is believable, too. Case life on my Swift was far greater than in the standard chambering. I don't know if I got more speed, but the brass lasted a bit longer. In my last IMP gun remaining, a 30-06 IMP, I get no increase in speed worth the conversion and dies.

I have nothing against Ackley chambers really, Just don't tell me that a high intensity cartridge, now improved, is better than the parent round unless you bring me pressure and velocity data to prove it. Tel me it's kicka$$ round and that it shoots great and that you love using it,and I'll give you, and the cartridge, two thumbs up.~Muir
 
I can only comment on my limited personal experience of 243ai and 257ai having 22" and 24" barrels respectively and both ran at substantially higher velocities than was shown in reloading data for the parent cases.
Cant comment on the pressures apart from observation of pressure signs on the cases/primers .
 
JR: I knew Ackley to the extent that we corresponded regularly for a little over a year. It began with me disagreeing with him in a gunsmithing column in "Shooting Times" (US) magazine about forming .256 Winchester Magnum from 357 Magnum cases. He ended up writing to me personally and so the dialogue began. I later attended classes at Trinidad State College where he taught and did much of his research, tho he had passed away by then.

Within our correspondence, we discussed ballistics and eventually the Ackley shoulder. He believed that it promoted a more efficient burn but that is something that, with the exception of certain combinations of case shape and powder, has been largely disproved at last look. One of the reasons to look into the Improved shoulder was the availability of cheapo, slow burning military surplus powders. 4831 was sold from barrels in hardware stores at one time, and it was cheap. Guys were loading it in .22 Hornet and 222 Remington. There were many cartridges in which a case full of 4831 just didn't generate any pressures and low velocity. It was these cases that Ackley's shoulder benefited the most. A person with a bolt action 30-30 of good quality had two problems: the long tapered case that tended to blow the column of slow to medium slow powder down tube before useable pressures could be obtained (one of those special combinations I spoke of) and the small case capacity for these powders. The Ackley chambering solved these, or improved these to a great extent. Thirty-aught-six shooters could stoke their 06's a little more, even.

What Ackley thought a waste of time for practical applications was improving a high-intensity cartridge. A factory round developing maximum allowable pressures (and they are built to do so, trust me) can hardly be improved on by adding case capacity. If one sticks to the approved pressure limits, then you pour more powder into the Ackley chamber until you reach that pressure again. If the bullet and barrel length are the same, you should see little difference in velocity and of course, we already mentioned that the pressure was the same. Unless you have existing barrels rechambered with an Ackley chamber, it's impossible to realize unless you have a pressure test gun. Here in the US gunsmiths who specialize in rebarreling gently push customers towards longer barrels. That will give you velocity increases od substance. A buddy of mine just got a 243 AI with a 30 inch barrel. You bet! More speed!!

I believe that Ackley did much of his experimentation because he could. He had marvelous equipment and the freedom to use it. One of his students, Deward Finley of Raton, NM attested to that. I apprenticed with Deward who was a fine barrel man and an admirer of Ackley. One thing Deward told me was that, tho Ackley's books were popular, the real "skinny" on Ackley's chambers was written by Ackley for the Lyman Gunsite Company in their #43 (IIRC) reloading manual where he talks about the kind of cartridges that should be "Improved" and those which should be left alone. My coments above about hi-intensity cartridges mirror what he wrote there.

That anyone's "Improved" chambered rifle is a fine gun and a serious shooter, I have no doubts. My 220 AI Swift was a screaming tack driver and I have often wished for it back. That you get better case life is believable, too. Case life on my Swift was far greater than in the standard chambering. I don't know if I got more speed, but the brass lasted a bit longer. In my last IMP gun remaining, a 30-06 IMP, I get no increase in speed worth the conversion and dies.

I have nothing against Ackley chambers really, Just don't tell me that a high intensity cartridge, now improved, is better than the parent round unless you bring me pressure and velocity data to prove it. Tel me it's kicka$$ round and that it shoots great and that you love using it,and I'll give you, and the cartridge, two thumbs up.~Muir

Very interesting reading, thanks for that.
 
JR: No problem. That was 30 years ago and I often wish I could find the letters. Four moves and a divorce got them packed away someplace. I did win my argument about reforming 357 when I mailed a few of the 25 caliber cases I'd made to him. In return, I got a post card with an exclamation point on it. That was the last thing I got from him.

bbrc: I built a couple of 257 Roberts IMP for some folks in New Mexico to use on antelope. They were good shooters and the customers were happy with them. I still have the reamer I used!~Muir
 
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