Prepped: Case sized, neck opening chamfer, bronze brushed internal neck...
+ Flash Holes: Prepped, like above, but Lyman tool used to de bur inside of case, primer hole opening.
No prep: Cases only full resized, nothing else.
2 groups on left, prepped, 2 groups in middle are prepped + Flash hole de burred, and 2 groups on right is full resize only, no prep.
Obviously, the "prepped" is going to be better than the no prep, over time, and in most all tests, because its simply more consistent.
But its hard to explain why, consistently, BOTH groups with flash holes de burred, were worse, not just worse, much worse.
And yes, 22 grains of Benchmark with 77 SMK @ 2.255 is a good load, and yes its more accurate than the beloved 23.3 grains of XBR 8208. However, that load is good, and has its place, as its over 100 FPS faster of note...
Results:
Benchmark 22.0 Grns 77 SMK
Prepped: 2612 FPS, 10 SD
+ Flash Holes: 2607 FPS, 18 SD
No prep: 2594 FPS, 15 SD
8208 XBR 23.3 Grns 77 SMK
Prepped: 2721 FPS, 9.3 SD
+ Flash Holes: 2709 FPS, 14.9 SD
No prep: 2714 FPS, 17 SD
With AR15's? Just prep your brass, don't worry about elaborate primer pocket this or that.