Just because you have another scope of the same model and make doesnt mean the one in question isnt broke. Swap them out and see what happens. If the other scope works on this same rifle then you know the scope is the problem. 5' groups are never the fault of the rifle. Even factory ammo should give you 1.5 inch groups out of that rifle. Its a simple way to find out if it is inded the scope thats the problem. The reason you hear that the scope is probably the problem is because about 100% of the time it is.

El Lobo