I use 3 on heavy recoiling guns. Some guys use 4. 50% more support and grip friction around the tube. I have seen scopes flex or slip with 2 rings. I like 2 in the front as the moment arm produced by recoil is greater away from the fulcrum of the grip. I also mount scopes with the scope turret front pushed tight against the mid ring to prevent the scope from creeping forward under recoil.