Intrigued by Ackley improved cartridges
- Thread starter fatelvis
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Brians356
Gold $$ Contributor
Not true. 280 AI only gains 3.5% velocity. But it is probably neck and neck with 257 AI for popularity.
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That is .257 Weatherby territory the minus boiler room space and massive freebore. I would not recommend trying to hit that speed.
For sure. I'll let the cases tell me when to stop.
Brians356
Gold $$ Contributor
That's a bit optimistic, Sierra lists 3400 from a 26" tube. Anything from Ackley's own data will go a step beyond. If you really want to drill into it, give Paul Box at Sierra a call. He ran all the AI tests in their manual, and doesn't mind chatting about them. Sierra doesn't publish the pressure numbers, but Paul has dug out some for me from his logbook.
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I have been told that for every 4% volume increase a 1% velocity increase may be realized. I have both 6mm Rem & 6mm AI. The 6mm AI has about 10% more capacity than the standard 6mm Rem.
With both loaded with 87 Vmax bullets, IMR 4831 powder, CCI 200 primers, Hornady 6mm Rem brass. AI velocity 3460 (26 barrel), Rem velocity 3305 (24 barrel), another 50 fps added to compensate for the 2 inch shorter barrel or 3355 fps for the Rem.
Doing the 4 to 1 thing: Assuming the 6mm AI has 10% more capacity than the 6mm Rem, 10%/4% = 2.5% (% more for AI): 3355 fps * 1.025 = 3439 fps.
The 4 to 1 ratio thing appears to be a good approximation. 3439 fps calculated for the AI compared to 3355 for the Rem (50 fps added to equal AI 26 inch barrel) AI was chrony'd 3460 fps.
Various members would probably load hotter and get higher velocities. The velocities shown gave at least .5 MOA accuracy and often better. Both rifles were evaluated at the same time. The Sierra manual for the 6mm AI gives 3400 fps using a max load of IMR 4831 and a 85 grain bullet. I squeezed another 60 fps with no bad indications using the same IMR 4831charge weight but with the 87 Vmax. Both rifles had 6mm McGowen barrels, 26 10 twist 6mm AI, 24 8 twist 6mm Rem.
With both loaded with 87 Vmax bullets, IMR 4831 powder, CCI 200 primers, Hornady 6mm Rem brass. AI velocity 3460 (26 barrel), Rem velocity 3305 (24 barrel), another 50 fps added to compensate for the 2 inch shorter barrel or 3355 fps for the Rem.
Doing the 4 to 1 thing: Assuming the 6mm AI has 10% more capacity than the 6mm Rem, 10%/4% = 2.5% (% more for AI): 3355 fps * 1.025 = 3439 fps.
The 4 to 1 ratio thing appears to be a good approximation. 3439 fps calculated for the AI compared to 3355 for the Rem (50 fps added to equal AI 26 inch barrel) AI was chrony'd 3460 fps.
Various members would probably load hotter and get higher velocities. The velocities shown gave at least .5 MOA accuracy and often better. Both rifles were evaluated at the same time. The Sierra manual for the 6mm AI gives 3400 fps using a max load of IMR 4831 and a 85 grain bullet. I squeezed another 60 fps with no bad indications using the same IMR 4831charge weight but with the 87 Vmax. Both rifles had 6mm McGowen barrels, 26 10 twist 6mm AI, 24 8 twist 6mm Rem.
I bought in on all this AI stuff a few years back. I have a 243 AI and the 257 AI and while I had some small velocity increases myself along with 99% of other people will not be able to even notice it. It's not worth it in my opinion, for most. JMO
Just Shoot.
Just Shoot.
Depends on barrel length and twist. As long as you don't get stuck with a slow barrel 3500 in a 10-twist is very attainable.Chamber up a 12 twist with a 100 NBT over RL-25 and expect speed well north of that.
Performance Gain over Factory Ackley Comment 222 Rem. Mag. Ack. Imp. About 5% more powder capacity More useful if necked up to 6mm 219 Ack. Imp. Zipper 350fps above top 45-gr. factory Zipper load Recommended, but use 30-30 brass post-WWII 22 Swift Imp. Better extraction, case life Mechanical advantage with velocity equal to Swift 22-250 Ack. Imp. 50 to 100 fps, case life Use Swift data and buy RCBS dies with 40" shoulder 22 Sav. H.P. Imp. 300-400 fps with 70-gr. 228-cal. bullets One of best 22s with heavy bullets 243 Ack. Imp. Extraction, case life Mechanical advarltage; originally a customer request 244 Rern. Ack. Imp. Very little gain in any bullet weight Auth. note: use RCBS 6mm Ack. Imp. 40 in 6mm rifles 25-35 Ack. Imp. 500-600 fps with 100-gr. bullets Recommended, use 30-30 brass post-WWII 250 Sav. Ack. Imp. 300-400 fps with 100-gr. bullets Recommended, Ackley's all-time favorite 257 Robts. Ack. Imp. 300 fps with 100- or 120-gr. bullets Recommended. Ackley's "all-around" cartridge 25-06 Rem. Ack. Imp. About 200 fps with 100-gr. bullets Not recommended, despite customer success. "Overbore" 270 Win. Ack. Imp. Little or none with more powder Not recommended, factory 270 is better 7x57mm Ack. Imp. 300-350 fps with 140-gr. and 200-250 fps with 175 Recommended, more useful to avg. shooter than 7 mags 280 Rem. Ack. Imp. 250 fps with 140-gr. bullets Recommended, 7 mag veloc. in '06 case 30-30 Win. Ack. Imp. 250-300 fps with 150-gr. bullets Recommended, excellent for lever guns 30-06 Spfld. Ack. Imp. 100-150 fps in any bullet weight Recommended, equal to 300 H&H 30-40 Krag Ack. Imp. 500 fps with both 150s and 180s Good, but not many rifles can use. Hot 348 Win. Ack. Imp. 200-250 fps above 348 factory load Recommended, better case life, less thrust 35 Whelen Ack. Imp. 5% powder capacity, 100-150 fps in 200s, 225s. 250s Recommended, flexible big game cartridge.
This is out of Ackleys Book
This is out of Ackleys Book
AckleymanII
Gold $$ Contributor
6/250 AI exceeded the 243 Win loads that I shot in other rifles, 95% of the 243 AI. Some of the powders available today may change those ratios.
My thinking is rounds like those based on the .308 W yield minimum gains when made into AI rounds as the body taper is only slightly modified leaving only the shoulder angle to be increased to 40*. The volume gain for the .308 W based rounds including the .243 W, .260 R would only be about 5%.
Rounds having tapered bodies like the .22-.250, 6mm Rem, .257 R, would gain more capacity when AI'ed, like close to or about 10% with little body taper & 40* shoulders.
I was disappointed when I looked at the Nosler manual & saw the .280 AI gained only 4% capacity over the .280 Rem but since I have 2, .280 Rems I feel better.
The .223 AI is popular & could be considered a worthwhile gain. Popular AI type rounds like the 6mm AI, .257 AI, & .280 AI are popular because of real velocity gains. But in the .280 AI this is probably because it is loaded to higher pressures. I don't hear much about the .30-06 AI but my guess is with 150 grain bullets & H4350 good velocity gains could be realized.
Other stuff like less case stretching should be considered. I like my 6mm AI, it gets over 100 fps more than my 6mm Rem and the extra capacity lets me use Re23 with 87 grain bullets and that load might boost the velocity gain.
Rounds having tapered bodies like the .22-.250, 6mm Rem, .257 R, would gain more capacity when AI'ed, like close to or about 10% with little body taper & 40* shoulders.
I was disappointed when I looked at the Nosler manual & saw the .280 AI gained only 4% capacity over the .280 Rem but since I have 2, .280 Rems I feel better.
The .223 AI is popular & could be considered a worthwhile gain. Popular AI type rounds like the 6mm AI, .257 AI, & .280 AI are popular because of real velocity gains. But in the .280 AI this is probably because it is loaded to higher pressures. I don't hear much about the .30-06 AI but my guess is with 150 grain bullets & H4350 good velocity gains could be realized.
Other stuff like less case stretching should be considered. I like my 6mm AI, it gets over 100 fps more than my 6mm Rem and the extra capacity lets me use Re23 with 87 grain bullets and that load might boost the velocity gain.
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