Well...in so far as the grain I guess. I usually shoot Federal AE223 for plinking. I want to try the Blackhills bulebox that Gander Mountain has got. But what it the highest grain a 1:9 twist barrel can take for accuracy and performance?

Ken

Some people will sit here and give you the ammo oracle link, but I'll tell you what I have the best results with.

1) 79gr. Match handloads from www.tsgunsandammo.com
2) Black Hills 60gr. from cheaperthandirt.com
3) Winchester 45gr Varmint from Wal-mart


Thats my top 3

Wes

Edit: This is out of a 1:9 twist 24" chrome lined barrel.

HERE

For my best resutls from a free float 20" stainless steel HBAR:

1) 52grain Match Black Hills
2) 40grain Nosler Ballisitic Tip Black Hills
3) Winchester 45grain Varmint

I have shot 68grain Black Hills out of it without ill effects (7" change in POI @ 100 yards to the right).

My typical results are 1-1.5MOA from 50 yards out to 300. Most of that is the idiot behind the trigger (me).

Best bet, Grab a box of each that is locally available and in the price range you want. Then go try them.

I have a 24" chrome-lined barrel with 1:9 twist, and I tell ya, I can feed my AR anything and drill tacks. I've shot everything from 40gr to 72gr and they all easily group sub 2 inch at 300 yards. I've tried every brand my gunstore has (just for fun) and the only thing I ever had a prob with was that CRAP BROWN BEAR.
I usually shoot 55gr acrossed the board for target and varmint, though 40gr for p-dogs works beautifully. I have a buddy who is in the Marine Corps and match shoots and says his 1:9 twist DPMS can be fed 79gr and still drill shit at 500 yards.

There is no "best ammo" for a 1/9 twist barrel.  All guns will behave differently with different kinds of ammo.  Just try a bunch of different types and see what is most accurate out of your rifle.  1/9 should stabilize anything from 40 gr. to 69 gr. so have at it.