Years ago before I retired I owned a Ruger Scout Rifle and a Mossberg MVP but when I retired I got rid of most of my guns, I am thinking on putting together a AR style scout rifle, I have at present a A2 lower ar15 and a 20 inch 5.56 upper like I used to carry in the army just legal I am thinking of using a 300 black out upper ( could be used to hunt Deer ) or what other cal would you recommend