Problems trying to get a Rock River to group

[Utah Shooter]

I am not sure what the issue can be. I do know that RRA has a warranty on their products. I wished yours shot as well as my Predator Pursuit does. I have no complaints and more often than not out shoot the guys at my range with it. It will shoot 50 FBHP's, 52 FBHP's, 65 FBHP's, 68 BTHP's, 69 BTHP's and 75 BTHP's sub .500

 

[ar15topgun]

Do not continue to use the thin cup standard primers in your ar. Slam fires are known to happen using them. SRM primers are not hotter in charge but have a thicker cup to prevent slam fires. If I were in your position I would try touching up the crown. There is no reason as to why it shouldn't shoot bug holes at 200-300yds.

 

[Gr8ful]

Rock River has a 3/4 MOA warrenty. I'd talk to them.

 

[yukonal]

My belief is that your bullets are ever so slightly damaged by the fast twist that some of them are affected by dynamic instability. Some are not or are affected to a lesser extent.

You say that you load works fine in a bolt rifle of the same caliber, I will say that there is a great chance that bolt rifle has a 1:12 twist, which is much more appropriate for these thin-skinned bullets.

I have three 8 twist Tikka's that will put every 50 and 55 grain V Max in the same ragged hole at 100. Cloverleaf's at 200. They stabilze just fine.

And I don't think your brass is an issue. I recently posted my results of weighing about 600 cases of LC brass from 2012 down to the 80's. They were all within a grain or less.

Guess you gotta start messing with bullet/powder combo's. That's what keeps it interesting.