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Ackley Improved???
- Thread starter jgcoastie
- Start date
Most loading manuals have cartridge drawings and many show some AI versions,so you can compare.
What PO did was make a different chamber reamer with the juncture of the neck and the shoulder in the same place,but the juncture of the shoulder and the case body is moved forward by increasing the shoulder angle to 40deg.
Typically the case body taper is reduced,making a straighter case.
The juncture of the neck. and shoulder provides a headspace feature to hold the brass against the bolt face.
So a standard load is fired in an AI chamber,no problem,and what comes out is an AI case.In hotrodder terms,bored and stroked comes pretty close.
There will be some increase in case capacity,and some increase in performance,and some suggested improvements in brass life.
Some cartridges that gain from AI might be the .250 sav,.257 Rob,7x57,280 and 30-06 (in heavier bullets)
One does have to go through the fireform process,and it should not be assumed an AI reamer can just be run in a standard chamber and you are good.It has to do with a full chamber cleanup and having that little headspace feature come out just right.A short chambered rifle or setting back the bbl a bit or a new bbl might be options.
It is something that works,I like my .257 AI,but the AI is not for everyone.
There are standard cartridges to do anyting well today.Still,if you are a little oldschool and want to fool with it,you may really like it.
What PO did was make a different chamber reamer with the juncture of the neck and the shoulder in the same place,but the juncture of the shoulder and the case body is moved forward by increasing the shoulder angle to 40deg.
Typically the case body taper is reduced,making a straighter case.
The juncture of the neck. and shoulder provides a headspace feature to hold the brass against the bolt face.
So a standard load is fired in an AI chamber,no problem,and what comes out is an AI case.In hotrodder terms,bored and stroked comes pretty close.
There will be some increase in case capacity,and some increase in performance,and some suggested improvements in brass life.
Some cartridges that gain from AI might be the .250 sav,.257 Rob,7x57,280 and 30-06 (in heavier bullets)
One does have to go through the fireform process,and it should not be assumed an AI reamer can just be run in a standard chamber and you are good.It has to do with a full chamber cleanup and having that little headspace feature come out just right.A short chambered rifle or setting back the bbl a bit or a new bbl might be options.
It is something that works,I like my .257 AI,but the AI is not for everyone.
There are standard cartridges to do anyting well today.Still,if you are a little oldschool and want to fool with it,you may really like it.
Loading data will tell you what the performance difference is between the standard configuration and the AI configuration.
But, there are often TWO factors at work to create the advantage. The obvious one is the increased case capacity. But, that really isn't much. ALL other factors being equal, the increase in velocity is approximately the 4th root (that is, the square-root of the square-root) of the charge increase, both measured as ratios. For example, a 5% capacity increase gives about a 1.2% velocity increase.
But, many reloaders ALSO increase pressure in the AI configuration. This is especially true for cases like the 7x57 that fit old guns and have old pressure standards to protect those guns. There is no worry that a hot AI cartridge is going to be fired in an old standard configuration gun , because it won't fit. So, often the load data also reflects a pressure increase, which is a bigger factor in velocity differences. A pressure increase creates a velocity increase that is approximately the square-root of the pressure increase, again figuring both as ratios. For example, an increase from 46,000 CUP to 52,000 CUP is a 13% pressure increase and will produce about a 6% velocity increase.
SL1
But, there are often TWO factors at work to create the advantage. The obvious one is the increased case capacity. But, that really isn't much. ALL other factors being equal, the increase in velocity is approximately the 4th root (that is, the square-root of the square-root) of the charge increase, both measured as ratios. For example, a 5% capacity increase gives about a 1.2% velocity increase.
But, many reloaders ALSO increase pressure in the AI configuration. This is especially true for cases like the 7x57 that fit old guns and have old pressure standards to protect those guns. There is no worry that a hot AI cartridge is going to be fired in an old standard configuration gun , because it won't fit. So, often the load data also reflects a pressure increase, which is a bigger factor in velocity differences. A pressure increase creates a velocity increase that is approximately the square-root of the pressure increase, again figuring both as ratios. For example, an increase from 46,000 CUP to 52,000 CUP is a 13% pressure increase and will produce about a 6% velocity increase.
SL1
crowbeaner
New member
I like the term "bored and stroked"! Like a 383 Chevy mouse motor. If you want a "hotrod" have a 22/243 AI made up. It's the 243 AI necked down to .224 with no other changes. Close to 4500 fps. with flyweight bullets; long (26+ inches) are best with a 1-10 twist. P.O. Ackley knew his stuff.