My barrel is a 28" Benchmark 3 grove 1:12 barrel, the contour is a copy of the sendero, it has a 2" long muzzle break adding 2", for an overall length of 30". I shoot the Hornady 30 cal 208gr AMAX pushed to 3200 fps using US869. the groups are sub 0.5 moa.
I did go thru my brass and debur the primer flash holes, uniform the primer holes, trim to length, and turn the necks to a uniform thinkness.
I have not found that it is necessary to ream the inside of the necks yet do to brass flow.
My brother has a Rem M700 LSS in 300 RUM, he shoots RL-25 with a Nosler 180gr AB @ 3400 fps into sub 1 moa.
Sometimes with light bullets and low end powder charges, you will get irratic ignition and pressure, this will screw up your groups.
I recommend you switch to +180 gr loads and continue developing your loads.
FWIW, I used Hornady 150gr bullets to fireform my brass and break in my barrel. I did not pay a whole lot of attention to groups sizes with those loads, just the patches coming out the end of the barrel. I think I had 50 rds into a 2" group that day. I used old 4831, and 20 yr old primers, saving the new ones because they were hard to come by this time last year.
Good luck - take your time and make sure all of the screws are tight on your rifle. If you want to sell, my son is looking for one.
