Bigcat, Roy is shooting US 869. I have a 115 gr load with that powder and the 300 gr Smkhp that chronographs 2780 avg velocity. The load I'm zeroed with is 110 gr of H-5010 and it is the one that averages 2760 fps. It also has single digit standard deviation. With your brake, the effective length of your barrel is probably only 25 1/2" or so. It is not likely that you can get 2770. I think you would have to push it to get 2650. I have 27 1/4" of effective barrel plus a home made brake for an overall barrel length of just under 29".
I routinely set my first screen at 7 yds to minimize muzzle blast and shockwave error. It makes the shooting window smaller, but doesn't rock the skyscreens as violently.
You're not using a B/C of .8 are you? Sierra downgraded the B/C awhile back to .7 something.
If you shoot it across another chronograph, let us know the results.
Texas State Rifle Association Life Member
NRA Endowment Life Member
A big fast bullet will beat a little fast bullet every time