I've read topics on this forum consistently for a few years now. The consensus seems to be go for a 16" barrel at the longest. It seems like an 18" offers a pretty solid velocity gain, potentially a rifle length gas system, and not too much longer than a 16. You can even put a standard A2 flash hider on it versus a long surefire suppressor brake/mount, keeping it just a little bit shorter. It's quite a bit longer than a 14.5 and especially so compared to a 10.3 XD but I am not clearing rooms and how many of us are?

If I have a goal for this rant it would be to get BCM to make an 18" hammer forged barrel. And other manufacturers to make a rail for a longer barrel, or more options like a KAC FF RAS behind a FSP. I get that 11.5's with suppressors are cool now, but other than the A2 stock, I think the M16A4 is a pretty solid rifle that gets bullets moving quick, sort of the point of the .224 caliber bullet.