Originally Posted by
levib
From what I understand, 5.7 carries much less power than a 5.56 round. Bullets that break into little pieces are called frangible, and have little to do with what caliber you're talking about inasmuch as you can have a frangible bullet on any caliber round. Frangible is nice for shooting steel targets and arguably for personal defense. It might be necessary for using 5.7 for defensive purposes, because frangible ammo expends all of its energy on contact instead of spending a good amount of it in penetration through your target.