No semi-auto will keep up with a bolt action for varmint use.
Because the law says so. Why do you think they might be restricted?
Depends on the rifle. I have AR10 rifles that shoot .5 moa with match ammo. This is in there with a good quality tactical rifle for accuracy.
There are AR-15 rifles (Les Bauer) that are known to shoot well below .5 moa. Some have even made claim to around 1/4 moa. If the AR platform wasn't restricted it would be the dominant varmint rifle. A bull barrel and match trigger turn these rifles into very accurate semi autos.
I agree mini14 target (But get the trigger done, it sucks in stock form), Then the SL8 and the Swiss Arms. The Tavor might work for varminting. It showed some promise with the right ammo. A varmint heavy barrel version of the Tavor would be fantastic along with a lighter trigger. I'd buy another one.