A while back I wrote a bit about some new(ish) Federal .300 Blackout 190-grain subsonic

ammo I tried.  Quite accurate at 30 yards, but definitely not subsonic.  Then, when I tried it at longer range, it wasn't anywhere near where my other subsonic landed.  Well, yesterday had the chance to go to the outdoor range(Shooting as God intended, outside and not quite melting).

50 yards, first three held on the center target

Three rounds about touching, center and about 3" below POA, just about identical to my handloads.  
And no, I have no idea why I couldn't see where they were hitting before.  Second three on lower left using the first stadia line for aiming, just about dead on.  Considering it's been a long time since any rifle work, and another excuse or two, not bad at all.

So I moved to a 100 yard target, used previously on another rifle/cartridge.  Target was the lower left, first round was with that first stadia line to aim, in that oval.

Second was fired using the second stadia line, 6" high.  

And no I have no idea why I couldn't spot the impacts the last time I fired this stuff.  Put this down to brain trouble, my excuse at least.

Velocities
1089

1081.4

1061.4

1079.8

1079.2

Average 1078.2, standard deviation 9.1fps.  This is from a new box from the original, I'd say whatever caused that first one to be supersonic was dealt with.  Or I messed up my counts/settings.  Ah well, good reason to do it again.

Checking notes, with handloads using the Hornady Sub-X bullet, my aiming point at 100 yards was using the second stadia line, which put it 4" low at 100.  So this appears to be a much flatter trajectory with that Federal Fusion Tip Bullet.  I need to try these two side by side on a day when it's not as hot and my various body parts are not telling me "Time, you need to put it all away now."