.308 Win Ackley Imp ?

[Gman]

I am considering building a .308 Win Ackley Improved for mid range score shooting. (out to 600 yards) I can't find out much info on this chambering. Can anyone tell me how many more grains of powder I will gain over a standard .308 Win ? The 17 lb rifle will be wearing a 30" HV barrel with a brake, pushing 155 gr Scenars. I am looking to squeeze out the most velocity, with less recoil, than a .30 caliber magnum. Thanks in advance.

 

[2644ever]

You could try this:
This is a project I tried last year as an alternative to the Ackley Improved configuration
http://img43.imageshack.us/img43/493/308shortneck.jpg
How do you do that? Just put a .308 pilot on a match reamer in .243 win and push it inside a .308 win chamber about .15" deeper. Next, neck up any .308 case to .338 and resize the neck in a .308 Win die with that same .15" gap between the shell holder and the die base, in order to create a false shoulder et voila! And the icing on the cake is that you keep your regular .308 dies and don't need no fancy Ackley reamer or dies.The net gain is about 3 grains of water, because I (wisely?) chose to keep the neck no shorter than 2/3 of a caliber. A 4% volume increase doesn't look like anything to write home about but it could be helpful if you have to deal with both a short magazine and a short barrel as was the case with the rifle I modified.
Of course you could improve on this one by feeding the .243 reamer a little further, after all the 8x33 Kurz works beautifully in a fully automatic rifle despite the shortest neck ever...

Otherwise the Ackley Improvement provides about 2.5 grains in supplement...

In both cases, the best results will be obtained with N 540.

 

[hogan]

If you are looking for most you can do w/o resorting to magnum boltface while using a case shorter than .30-06, the .30/284 would be the ticket. I am sure you'll get some nice gains from the AI'd .308, but nothing exceeding the .30-06. If you want more than .30-06 might consider the .30 Gibbs.

Good luck!