Ok lets go "punch for punch" I'll go first with my peasly .223 rifle and then afterwards you can shoot at me with any caliber you want.
nah... You both can compare how heavy your ammo weighs versus how many rounds that equates to...
You can then both load up your weapons and do timed live fire and see who has swap magazines first.
Nothing against say 7.62, but for the swiss army knife of rifles, I'm sticking with my AR in .223.