One of the things I would look at is what range are you expecting to possibly be engaging targets at? If you are talking about clear fields of fire going out six hundred plus yards then a real rifle caliber would be called for. If you are talking about a cabin in the woods with a maximum range of one hundred fifty yards things are a little different.
Would some pistol caliber carbines like the Hi point work?
Would some pistol caliber carbines like the Hi point work?