Originally Posted By: waterweasleI was liking the idea of using a plastic shim( if I ended up shimming) till I thought of your exact reasoning of plastic changing with heat, I think I'll get a 20 or 30 moa base and leave it at that, thanks guys
If your receiver is not "level" as described above, you will still be loading the 20 moa base with some unwanted strain if you don't shim between the receiver and base. I only use Leupold bases and scopes so when I called them with this problem, they send me a sack of shims. I've also seen them for sale at Brownells and used the pop can shims as well on my P-14. You want a straight and level surface to put your equipment on whether it is a scope base, pump or wifes stove 
