Re: Savage FP10 Mount Problem
First, there is no standard in anything in the "gun" world. Every thread is a bastard thread. THE only thread you will find that you can actually get a screw to match at a hardware store is the ones that hold the action to the stock, and usually, they need a special head.
My guess is that they put #8-40 screws in instead of the chinsy #6's that you usually get with your bases. Simple enough, just get the right bases to match. No doubt, you will find they are larger than you expected. All the screws can be had from Brownells. Expect to pay $15 for 12 "assorted" screws of which you can use 4.
Your smith should have had screws. Mine does, by the bushel. Mine gave me a whole box full for my gun when I needed some. I took a few and gave the rest back.
I'm sure, whatever Savage did, it was on purpose. No mistake. Look at Natchez Shooters Supply and check the mounting charts for your gun to get a base to match. You'll be on your way.
If you have something that you disassemble and reassemble enough times, sooner or later, you'll have two!