I like how Jeff at Protein Wisdom put it...

Semi-automatic rifles can be used just fine for hunting.  Though typically they are less powerful than larger-game hunting rifles, which tend to use more powerful rounds.  All of which is beside the point, because the 2nd Amendment was never meant as a permission slip from some Iowa douche to allow you to go hunting.  It was instead meant explicitly as a check on Iowa douches who would presume to tell you what you can and cannot use to protect yourself against the kinds of Iowa douches who lurch toward tyranny and try to take away a natural right by the stroke of their douche pens.