September 28th, 2008

6BRX: Long-Term Accuracy and Barrel Life Report

For two years, Forum member John Skowron (John708) has been campaigning a 6BRX, built by Nat Lambeth (RustyStud). You’ll find the full history of John’s 6BRX project in this Forum Thread. With this rifle, John was the overall 1000-yard winner at Butner in February 2007.

6BRX 6BR improved

The 6mm BRX is based on the 6mm BR cartridge. The shoulder is moved forward, but the shoulder angle and case taper is the same as the parent cartridge. This way you can use standard dies for most purposes (although it is a good idea to have a custom full-length die so you can size the entire case body). Many of our readers have been interested in the 6mm Improved (BRX, Dasher etc.), but they’ve wondered about case durability and barrel life. John has answers for those questions:

6BRX Case Life
Case life running the Berger 105s at 3000+ fps is 14-15 reloads. Brass was discarded when the primer pockets became too loose. The 6BRX brass OAL after fireforming is 1.56″. Max OAL for the 6BRX is 1.58″. The brass never stretched enough to require trimming before discard. Another plus for the 6BRX and Lapua brass. By the way don’t even bother with Remington-brand 6BR brass. The primer pockets were so loose after my standard fire-forming load I had to trash all the cases. Stick with the good stuff, Lapua.

6BRX Barrel Life
Here are Skowron’s comments as his round count increased:

2750 Rounds: I now have 2570 rounds through my 6mm BRX. I was just at the range today doing an accuracy test. I shot two 10-shot groups at 100 yards, one with 105gr Bergers, and the other with 107gr Sierras. Both were identical 0.44″ 10-shot groups. Not bad for a rifle with 2500+ rounds through it.

2900 Rounds: I now have 2900 rounds through my 6mm BRX. I was doing some load testing with the new 6mm Berger bullets. I compared them with my existing comp. load in my 6mm BRX. The 105gr Bergers, jammed .015″ into the lands, with 31.5 grains of Varget and Fed 205s are still shooting .45″ 10-shot groups at 100 yards. Velocity is 3060 fps. I don’t know how long this Broughton barrel will last, but I’m amazed that it’s lasted this long.

2950-3044 Rounds: I had virtually no throat erosion until I reached 2900 rounds. After 2900 rounds throat became noticeably rougher on cleaning and groups opened up. 10-shot groups with match ammo were now .53″ (compared to low fours before). At 2950 rounds the groups ran .58″. At 3044 rounds, the groups opened up to .7″. That’s not enough accuracy for LR work.

CONCLUSION: Barrel life with competitive accuracy was 2900 rounds with this gun.

Achieving this barrel life goal pretty much completes my 6mm BRX project. I’m now shooting a cartridge that has the same or better barrel life than the 260 Rem, it’s more accurate, with essentially equal wind drift. [Editor’s Note: Richard Schatz recently won the NBRSA 1000-yard Nationals with a 6 Dasher, a similar 6BR Improved cartridge, but with a 40° shoulder. Richard’s barrel had over 2000 rounds through it.]

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