Rather than look at weapons we must first focus on ammo. Look at ammo prices first, see what is cheap, then find C&R firearms that shoot that kind of ammo. A small list that I can think of off hand for cheap ammo are:
Wow guess I cant think of anything else!!! Most mil surplus firearms really are not cheap to shoot unless its in one of those calibers. For a little more you can add the cheaper surplus and russian made 30.06, 8mm, 6.5x55, 7.5 Swiss, and 7mm Mauser to the list. The Mosin Nagant is by far the cheapest thing to shoot.