Good article and it has a good conclusion go to a different bullet . Talk about fragmentation means little to certain groups . probably special forces and definitely us civilians . We can use hollow points , soft tips and other advanced defense loadings that sidestep alot if this . As for a round holistically and barrel length performance If you want SBR get . 300 blackout or 7 . 62 x 39 . My 8 . 5 in Galil Ace pistol only loses 15 % velocity vs a 16 in barrel and still puts more energy on target than 5 . 56 at least 75 yds . And it ' s still shooting a bigger heavier round with superior barrier penetration to boot . Certain rounds were made to excel at this sort of thing . 5 . 56 is not one of them . Real wish we had 9 x 39 .