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Intrigued by Ackley improved cartridges

fatelvis

fatelvis

Does anyone have a short, concise table showing the average velocity increase from standard to AI version for all cartridges? Just curious as to the % increase in each. Thanks guys
 
It really all depends on the parent case and how much taper it has. Some cases gain a higher percentage of case capacity than does others. Cases that are already fairly straight-ish and very little taper, such as the 223, 243/260/308 cases or the 06, will gain very little when you "improve" them but others, like the 220 Swift, Rem 6mm, 6.5X55 Swede, and 338 Lapua, have a lot more taper and will increase a much higher percentage.
 
fatelvis said:
Does anyone have a short, concise table showing the average velocity increase from standard to AI version for all cartridges? Just curious as to the % increase in each. Thanks guys
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Someone just posted this info in the last week or two on AS,
I will try to find it.
CW
 
B23 said:
It really all depends on the parent case and how much taper it has. Some cases gain a higher percentage of case capacity than does others. Cases that are already fairly straight-ish and very little taper, such as the 223, 243/260/308 cases or the 06, will gain very little when you "improve" them but others, like the 220 Swift, Rem 6mm, 6.5X55 Swede, and 338 Lapua, have a lot more taper and will increase a much higher percentage.
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You are exactly right! Most of the cases I have improved, I did it to obtain a better case design, not to obtain more velocity. Any velocity increase is merely the icing on the cake>>>>the "cake" is a better case design for what I do, which is F-Open.. "Generally" an "Acklyized" case develops a shade better accuracy and they cut W-A-Y down on case trimming, which I detest!
 
Don't have any tables showing the increase, but most cartridges will or can obtain anywhere from around 100-150 fps with the Ackley shoulders.
Main point going for it, is the less brass growing in length and trimming process.
I also like, and use several cartridges in the improved version that Parker had.
 
Low capacity cases with severe taper show the greatest velocity increase. 22 Remington Jet VS Super Jet is an example. As previously stated, cases such as the .308 Win result in very marginal speed increase.

Many people find that Ackley cartridges can be loaded to somewhat higher pressures due to reduced bolt thrust.
 
I believe "Ackley Improved" cases are a stroke of genius. Not because of any possible capacity gain, but because they produce a "proper" case shape with angles designed to minimize stretch or growth from firing and an ideal combustion process. It is always possible to get a bigger case to get more volume, if that's what one wants, but the AI design is truly an "improved" cartridge.
 
Years ago, I shot a 6/250 AI on Rock Chucks, p. dogs, and coyotes. I am surprised that the case has not been tried with 115's today.

I used the 6/250 AI for 70g with Win 760 at 3800 shooting tiny bug hole groups. I never did see a down side for the case or the load.
 
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Ackley hisself said that most of his conversions offered little in the way of performance gains. The one that offered the greatest performance improvement was the 25-35 WCFAI. The biggest advantage is what a previous post stated, case trimming will almost be eliminated.
 
The Pumpkin said:
Can just anyone design a case and call it an Ackley? Should credit be given to the cases PO did? You can call it improved or in my case I call it a NAFA. D
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One of the defining factors about Ackley’s is they are designed to headspace the parent case at the neck/shoulder junction so that they don’t have any case head separation issues when fire forming. Most but not all had 40 deg shoulders Along with fairly minimal body taper, but not straight without any taper. And technically only cases designed by P.O. Ackley are true Ackley’s but it has unofficially expanded to newer cases designed after his death that have the same parameters.
 
I believe this is what you are looking for:

http://gunloads.com/castboolits/attachment.php?attachmentid=28589&d=1295041970

It's a PDF file. I tried to paste it here, but the forum editor is confused by it somehow, hence the link.

Please consider: The improvement figures are for velocity, not case capacity. The "% increase" listings are somewhat misleading in several cases, since the parent cartridge velocities cited are the manufacturers' and often much lower than what an older cartridge may be easily pushed to in a modern rifle, while the AI velocities listed are what may be realized. If you read Ackley's books and inspect his reported velocities carefully, you may ken that he loaded to higher pressures than what most people consider prudent today. So the alleged improvement assumes a low factory velocity and an optimistic AI velocity.

For example, the "Factory Velocity" given for 250 Savage 100-gr bullet is only 2820. But the Sierra manual lists a maximum for 100-gr bullet at 3000 fps (custom Mauser, 24-in barrel.) The original spec for 250 Savage had the Savage Model 99 lever action in mind, and a conservative max pressure of 45,000 CUP was stipulated. To become the first commercial cartridge to reach 3000 fps in 1915, they had to employ an 87-gr bullet. (Sierra today lists a max of 3200 for that pill.)

Now consider the improved velocity listed (100-gr pill). In the list it's 3300, but Sierra 250 AI data tops out at 3200. The velocity improvement in the list is 480 fps, but Sierra's improvement is only 200 fps, and that from a 26" AI barrel!

Anyway, a 17% velocity improvement for 250 AI is not realistic if you consider what the 250 Savage is really capable of unimproved, and that Ackley's top improved loads tended to be questionably hot.
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brians356 said:
I believe this is what you are looking for:

http://gunloads.com/castboolits/attachment.php?attachmentid=28589&d=1295041970

It's a PDF file. I tried to paste it here, but the forum editor is confused by it somehow, hence the link.

Please consider: The improvement figures are for velocity, not case capacity. The "% increase" listings are somewhat misleading in several cases, since the parent cartridge velocities cited are the manufacturers' and often much lower than what an older cartridge may be easily pushed to in a modern rifle, while the AI velocities listed are what may be realized. If you read Ackley's books and inspect his reported velocities carefully, you may ken that he loaded to higher pressures than what most people consider prudent today. So the alleged improvement assumes a low factory velocity and an optimistic AI velocity.

For example, the "Factory Velocity" given for 250 Savage 100-gr bullet is only 2820. But the Sierra manual lists a maximum for 100-gr bullet at 3000 fps (custom Mauser, 24-in barrel.) The original spec for 250 Savage had the Savage Model 99 lever action in mind, and a conservative max pressure of 45,000 CUP was stipulated. To become the first commercial cartridge to reach 3000 fps in 1915, they had to employ an 87-gr bullet. (Sierra today lists a max of 3200 for that pill.)

Now consider the improved velocity listed (100-gr pill). In the list it's 3300, but Sierra 250 AI data tops out at 3200. The velocity improvement in the list is 480 fps, but Sierra's improvement is only 200 fps, and that from a 26" AI barrel!


Anyway, a 17% velocity improvement for 250 AI is not realistic if you consider what the 250 Savage is really capable of unimproved, and that Ackley's top improved loads tended to be questionably hot.
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Click to expand...

Thanks Brians356, thats exactly what I was looking for! And thank you guys for all the other attributes of the Ackley design.
 
Let's compare 250 AI to 257 AI, as it illustrates the sweet spot in case capacity and design occupied by 250 AI (and its cousin 6.5mm Creedmoor.)

The 250 Savage has a case capacity of about 45 grs, the 257 Roberts 55 grs or about 20% larger. Ackley improving the tapered 250 Savage yields about 11% more capacity, and about 8% more velocity. Improving the 257 Roberts yields about 9% more capacity but only 4% more velocity. These numbers allow the 250 AI to catch up with the 257 Roberts, and nearly catch the 257 AI, falling only about 100 fps short with lighter bullets, even though the parent Roberts started with a 20% capacity head start! Improving the Roberts runs up against diminishing returns from 25-cal bore capacity.
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