New 6BR: Love at First Group

Many Forum members are putting together their first custom or semi-custom precision rifle this season. These folks often ask us, “What kind of accuracy can I expect from my first 6mmBR?” Of course there are no guarantees, but a 6BR with a good custom barrel, good chambering job, and a nice bag-riding stock should be able to shoot well under half-MOA (1/2″ at 100 yards), maybe even approach quarter-MOA. Forum member Eric (aka Exercion) provided this interesting report on his new 6BR:

Love at First Group by Eric
Well, I took my new stick to the range for the first time today. It features a Savage single shot target action in RBLP configuration, 28″ Broughton 5C barrel, Sharp Shooter Supply Dogtracker stock with adjustable buttplate, and Nightforce scope.

Now, I have never owned a 6mmBR before, but from reading here and seeing them in action I decided to build one. Its main purpose in life is mid-range F-Class shooting, mainly at 600 yards, and if the winds are favorable, at 1,000. (I already have a 6.5 for “normal” conditions.) I am most grateful for all the info here, and especially the load data. I picked Reloder 15 under the 107gr SMKs for my first loads, starting at 29.0 grains, and proceeding in half grain increments to 30.0 grains. Jumped the bullets 0.015″. Ran the Lapua brass through the neck-sizer bushing die, and was concerned at the force needed to pull the expander button through the virgin brass necks but figured this was a once per case deal to round them out for initial loading. When I measured the runout on the loaded rounds, I was appalled as they had more wobble than anything I personally loaded before, but I kept reminding myself that this was the fireform/chronograph/scope and gun trial stage.

Three Shots in 0.335″ Edge to Edge
So off to the range this morning. No wind here at the house, so life was good … until I got to the range and the wind started to blow. So I set up everything, leveled the gun in the bags, leveled the scope to the gun, made sure the bore was in the center of the chronograph and bore-sighted. First couple of rounds were off to the right, so I moved the scope over 5 MOA and fired another shot, hit paper with it, so I shot 2 more and stopped because I couldn’t tell what was happening. A walk down to the hundred yard berm revealed a nice hole that measures 0.335″ at its absolute widest edge to edge! That’s the smallest 3-shot group I’ve ever fired with anything. I am so in love!

SDs Improve with Heavier Charge and Run-out Disappears
I kept going ’til I worked my way through my first 100 rounds.Given the conditions, I was more interested in the chrony numbers than group, (though 20-shot strings yielded nice quarter-sized holes) and found that as my charges got heavier the SD was coming down (the 30 grain load gave me an SD of 9). I can’t wait to see what will happen with some load tinkering, as well as bullet trials (have Bergers, Hornady A-Maxs, and Lapua Scenars waiting for the next trip). Also, as I had hoped, fire-forming “cured” the run-out problem. I ran the fired but un-sized cases over my concentricity tool and saw less than 0.001 runout on the necks now.