[FlyinBryan]

so far the heaviest ive loaded was a 68g bullet.

oddly, everytime ive gone to a heavier bullet, its been more accurate. so how heavy can i safely go with an ar rifle with a 16" 1in9 bull barrel?

[rcmodel]

Safely?
Any weight you can find bullets and reloading data for.

Accurately?
Most 1/9 AR's top out with the 75 grain Match bullets, but the only way to know for sure is to try them in your rifle. But many of them will be too long to function through an AR magazine and will have to be single loaded.

rcmodel

[Ridgerunner665]

+1 to rcmodel...

Mine shoots most 70 grain bullets just fine...but not the Barnes 70 grain TSX bullets (solid copper), they are a smidge too long, they tumble past 225 yards or so.

[NuJudge]

In a 20" barreled AR, I can not get anything heavier than 52 grain bullets to shoot well.

People say that some will shoot 75 grain bullets well, but my 1:9 does not.

[rcmodel]

52 grains?
Yikes!

You must have something very wrong with your barrel.

Even a 1/12 should shoot 55 - 60 grain one-holers.

rcmodel