I wouldn't give any thought to excess wear. That's mostly theoretical rather than a broadly observed fact. As to recoil impulse...I would hardly call a 5.56 carbine recoil "violent". However, the recoil impulse is a little softer with a mid-length IMHO, so other than a shorter hand guard, I see no reason to go with a carbine over a middie on a 16 inch barrel.

