Best bullet weight for my rifle

[racer88]

A newb question here. I may give competition a try in the near future. Handloading my own ammo is not feasible at this point in time. I see that Federal Gold Medal 223 Sierra Matchking comes in two weights: 69-gr and 77-gr. It isn't cheap ammo, so I'd rather not have to buy both (to compare), if I don't have to. Which is best for my rifle (see pic for specs)?

http://i1042.photobucket.com/albums/b425/racer88_bucket/Gun%20Stuff/ar-15-sniper_0001.jpg

Thanks!!

[Zak Smith]

Choose whichever one shoots better in your rifle. The 1:8 twist barrel can stabilize both.

[racer88]

Choose whichever one shoots better in your rifle. The 1:8 twist barrel can stabilize both.

Should have figured that, I suppose. :) Thanks.