Is there anyone "out there" who have any experience or knowledge about the .308 Win Ackley Imp. (40 degree)? Myself, and some friends are looking for the best cartridgedesign for short barrels (20 - 22"). It must not bee too hot, so that it erodes throats too fast (as the .243W. A. I. does) and it must be "efficient for its volume". My best example of such a cartridge is the 7mm 08Ackley Improved. I thought that a .30 cal neck would make this cartridge "more efficient" i.e. the .308W. A.I.?
I dont have any info on the 308 ai but BR shooters tend to shoot short stiff barrels, you may want to look into the 6PPC. The waldog also come to mind (I believe it is .125 shorter than the 6ppc.) These may interrest you. I don't know the intended use but if you would like more info on the BR stuff try www.benchrest.com
Andrew
Posts: 49 | Location: Texas | Registered: 23 August 2003
The "improved" version of the 308 isn't much of a improvement. You gain about 3% more powder volume so a increase of 1%to 1.5% in velocity. The only good thing about it is the 40 degree shoulder will extend case life.
Posts: 593 | Location: My computer. | Registered: 28 November 2001
Thank you very much for your reply, Navrunner and DanD. - I thought that the .308 A.I. would at least give as much volume increase as the 7mm 08 A. I. over the original case, - resulting in improved velocity averaging approx. 6% ... I guess there's a good reason for this cartridge not beeing mentioned that often.
A shooting buddy of mine had a rifle chambered for the 308 A.I. 40 degree shoulder. And in testing it he found the ONLY powder used that showed any substantial gain at all was N540. He was getting 3050 accurate fps with a 155 gr. bullet. from a 26" barrel. Yes I can get a little over 3000 with a standard 308 but it isn't an accurate 3000 fps.
The 7-08 Improved gets more capacity increase because there is more shoulder to blow out. It's a bullet diameter versus shoulder diameter issue. In other words you get even more capacity increase with a 243AI percentage wise.
Posts: 593 | Location: My computer. | Registered: 28 November 2001
A good, efficient "improved" cartridge is the 8X57mm Mauser Improved. It is about equal ballistically with the 8mm/'06, but uses less powder. In addition, there are now quite a few 8mm bullets avaiable to choose from!
