I've been working on load development for a new 6.5 Sherman Short that I had built by Ryan Pierce (Piercision), who did an awesome job. It's got a 24" Proof research barrel, 1 in 7.5 inch twist, and I'm running it suppressed. Running ADG brass from Sherman. Primers are CCI 200. I don't have a Lee FCD for this round yet, I suspect when it arrives I'll see the groups tighten up a little as I've experienced with other Hammer loads.
Here's what I've got so far:
H4831SC seated at 2.270 cbto
58.0 - 3085
58.5 - 3092
59.0 - 3132
59.5 - 3142
60.0 - 3169
60.5 - 3197
61.0 - 3232
61.5 - failed to record on LabRadar
62.0 - 3273, Pressure (ejector mark)
Also tried RL23 on the advice of Lance Kenyon. These were seated at 2.280 cbto to start.
57.0 - 3137
57.5 - 3129
58.0 - 3144
58.5 - 3205
59.0 - 3228
59.5 -3207 (this one was actually seated a little deeper, 2.275, hence less pressure.
60.0 -3259 No pressure signs, but stopped here.
I was seeing very consistent grouping with the RL23. The rounds with 58.5, 59.0 and 59.5 printed the cloverleaf lower left, this was at 200 yards. The 60 grain charge produced the flier:
Continued load development today. Its a little windy, 18-24 mph today at almost full value so I moved in to 100 yards to minimize the wind effect.
After trying different seating depths and powder charges, (it's evident the barrel is speeding up, at about 70 rounds through it as of today) settled on 58.7 grains of RL23, seated at 2.270 cbto. This produced an average of 3254 FPS with an ES of 31 and SD of 16. group about 1/2 MOA, photo below: