im kind of new to the ar world and i just wanted to know if the twist in your barrel should determin what kind of ammo you should shoot like will above a certain grain not function of ruin the barrel?

You can shoot any bullet weight however, the accuracy may vary.

1:9 will tend to shoot lighter bullets (<62gr) more accurately than heavier bullets, although there is no wieght at at which accuracy suddenly changes...it varies from rifle to rifle.

I can't post pix, or I'd post THE pic...someone will shortly.

Test the ammo in your rifle.  Shoot as heavy a bullet as you can with acceptable accuracy.  But you have to put in the trigger time and shell out the money for all the ammo.  No one can tell you what is "best" for your rifle.  Shoot and see.  Most 1:9 twist barrels will do OK with 75gr bullets, but 77gr will often start to key-hole.  If neither stabilize or have acceptable accuracy, then look at the 68-69gr offerings.

Please read the FAQ's up above and feel free to post any follow-up questions.