Is there a difference between 556 in a 16 inch barrel vs a 20"?

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>>34744555
I know there's a good chart somewhere showing rough fragmentation chances relative to velocity on regular fmj copper platedammo. (steel jackets probably hold together much better) And you can extend that fragmentation distance with that 20" barrel.
I shoot 556 out of a 23.3in barrel and I'll tell you right now that that extra velocity makes 556/223 melt through my hardened steel infinitely better than even steel cored(non AP) 762x54r at 100 yards. That 54r can't even do more than slightly dent it.
I don't have a 16" 556 gun to compare with, but that "should" knock it's velocity more in line with the 545x39 I'm shooting. And that can't penetrate my hardened steel, even with 7n6 ammo. It does better vs my thinner hardened steel than lead core 545, but still not much difference.

>>34744555
20 inch is more better for the same ammo

>>34744555
Massive. I have a 16 in sig m400 that's good. But my ar I built with a 20 in free floated fluted barrel can outshoot it by a lot