Not sure why you went there, what does the 300blk have to do with anything?
Sectional density on any 300blk bullet at reasonable speed is crap (110grn 30cal is .168, only worthy of varmints and small game), any bullet in the 300 with a decent Sectional Density (SD) is only gonna be trucking sub-sonic speed, so it can't really capitalize on its potential because of its small case.
Nothing in common with the 6.5's, other than a he11 of a lot of marketing turning yet another lack-luster cartridge into a pop hit. Taylor Swift and Lady Gaga sell a lot of tickets, neither of them for the sake of actual singing talent...