Before You Bubba-Up That Mosin-Nagant

...please do a bit of research to see whether or not it is a rare variant.

Yes, the total production was something north of ten million rifles and carbines. But that doesn't mean that there aren't some rarities out there. That rifle you bought could be worth a lot more than the $150 you just paid out for it at Herman's Bait and Booze.

But it won't be worth that once you take a saw to the stock and drill the receiver for mounting a scope.

Actually, this applies to all military rifles. Something like a couple of million Springfield M1903s were made, but there are some relatively rare ones out there. For example, there was a short period of time between when production was farmed out to Remington and when they started making the 03A3s. Some of the internal changes from the 03A1 to the 03A3 (besides the sights) were made during the last production of the 03A1 series. So while Grandpaw might have thought it was a good thing to shorten the stock and mount a scope on it, that rifle, unaltered, might be worth over two grand if he hadn't (rather than the $300 it's worth today).

A little bit of research before you go to town on your new milsurp rifle might be profitable.