Board Thread:Warhammer 40k General Discussion/@comment-211.26.90.118-20130804022732/@comment-8257990-20130804112128

Remember that Imperial rounds are likely much more high tech than modern rounds, they are probably made out of better materials, have a better AP value and chances are fired at a higher velocity.

Also besides explosion size Bolters are basically rapid fire RPGs, able to even break through Power Armour in one or two direct hits (I don't have to tell you how impressive that is).