Unknown for sure(probably Hart) 21" used BR barrel, .236 bore, 14T, 6 BRA with zero freebore or close to it(borrowed the reamer), non neck turned brass.
65g-68g benchrest bullets with .003 jam, .266 bushing, 30.3g of xbr 8208 shoots very, very tiny groups, day after day after day. Interesting that .268 and .267 bushings shot in the threes. Benchmark & H322, (old Scotland powder) I never found a bug hole load . Played with 205, CCI br-4, cci 450, and 7 1/2 was a hands down winner with no close contender. If the bullet does not jam, the group opens up.
I had just about given up on the barrel and was ready to toss it, and on a lark I tried the XBR 8208 hit a home run, real quick, then just a matter of fine tuning. 70g tnt shot some amazing groups with 30.0g xbr 8208.
With slow twists, I will reserve judgement as to whether or not this case is as easy to tune as a std 6 BR used as a varmint rifle with lighter bullets.