I don't have a Varmint Hunter, but I believe that most of the GAMO rifles have a scope stop that comes with the combo. You may have a scope shifting problem. The scope you have may be damaged by the shock from the springer's recoil. Also, I don't know how familiar you are with springer rifles, but most are hold sensitive in one way or another. There are a bunch of intelligent folks on the forum that will probably chime in on this. The GRT III should fit your rifle and it is one of the best upgrades that you can get. Gene and Paul (FIX) are two of this forum's tuners and I haven't heard a bad word about either's work. I have shot rifles tuned by both of them and they both do outstanding work. Welcome to the forum. You've found a great place.