one problem with doing an AR is the 3 inch sight height. Also IMO you want accuracy that is always sub .75, I shot a lot of varmints from 20 to 75 yards. having the scope super high above the bore complicates those shots. Also I shoot very small targets. accuracy and not excessive sight height are important factors. you say why shoot stuff that close. well the effects are pretty dramatic often times. besides shooting a rimfire is boring in comparison. Those 2 issues are why I wouldn't do a 17 fireball on an AR. not to mention the brass chucking. There are ways of dealing with that but its still a factor.
