Thread: Anyone played with 223AI?

Originally Posted by grandpamac

Greetings @kiwi303 and all,
First my apologies for having, along with others, hijacked your thread. Parker Ackley came out with his series of improved cases in the 1940's and 50's. The idea was to get a bit more velocity from the limited number of standard cases available at the time. Large increases in velocity were claimed due to the case shoulder shape but little of the data was chronographed let alone pressure tested. Much more recently actual pressure testing has dispelled some of the myth. The only cartridge I can think of that has been adopted as a factory cartridge is the .280 Remington AI. Hodgdon publishes pressure tested data for both the standard and AI versions. The AI version is loaded to a higher pressure and charge, velocity and pressure are all linear (form a straight line when plotted on a graph. A little number crunching indicated that the increase in velocity was around 35 fps for the AI over the standard version, not the several hundred fps claimed by some.
If you really like the look of the 40 degree shoulder then by all means go ahead but there is another path. The .223 is most commonly chambered in semi autos in the US and these have particular requirements regarding port pressure and it appears to me that current data has been dialled back for some powders due to this. Of the powders I have worked with AR2206H (H4895) seems to give decent velocity within published data where some later data for other powders struggle.
Best of luck and regards Grandpamac.

Ackley is dear to my heart. I have all his books and notebook.
Yes, a gain in velocity was a benefit but Ackley said himself, in his books, that velocity increase wasn't the main driver. Eliminating or minimising brass flow and constant trimming with the 40 degree shoulder was one on his main stated aims. Reduced bolt thrust by using a very shallow case taper was another benefit.
Also a lot of the Akleyised catridges didn't give worthwile velocity improvement at all.
And of course it has become fashionable to create an AI nowadays even though the man himself didn't create it. I shoot a 6.5x55bjai which was not one of Ackley's. Bob Jordan, the American gun writer created that one. Bob Jordan also wrote a very good article in the Precision Shooter some years ago analysing Ackley's efforts and the later ones created by others. Some of them offer virtually no velocity improvement. I cannot locate that article now. I am not sure where the 223AI sits.

PS: The 6.5x55bjai is one of the more successful improvements. I running 6.5/284 velocities, using slightly less powder than a 6.5/284, and have hardly trimmed cases to date.