With the 300BLK,your bullet speed AND associated energy/momentum levels drops off pretty fast when you start subtracting anything from a 16" bbl. . --- pruhdlr
The muzzle velocity, bullet drop, and energy charts don't bear that out. There is about 200fps difference with identical loads (regardless of the load) when fired with 9" and 16" barrels, and about a 200ftlbs energy difference. The bullet drop charts show about a 20 to 30 yd difference for equal drops from the 2 different barrels (480 vs 450 yards for 100" of bullet drop).
I won't argue the ballistic prowess of the 300 blk, only that there isn't a significant drop-off from shorter barrels. I think that is one of the reasons for it's popularity (along with the sub/super thing).
Disclaimer - I have a 10.5" 300 pistol, and a 16" Wilson Combat barreled (also pistol gassed) 300 rifle. While I have only shot them @ 100yds or so, I don't notice a significant difference in performance with identical ammo.