Looking for recommendations for a cheap air rifle scope for backyard plinking. I bought my son a Gamo air rifle that absolutely eats scopes for breakfast. I have gone through 3 Gamo branded scopes in a few months. In all instances the rifle makes the reticle do circus tricks - they end up every which way but straight. Good news is that my son shoots the heck out if, bad news is I can't keep it in service for him. A 4X or 3-9 is what I am looking for. Thanks