The Nagant revolver now, that's a pretty interesting piece. They're on the C&R list now btw. I'm not interested in them myself but some folks really like them.
They are fun to shoot, but the ammo is on the pricey side. You can buy another replacement cylinder and shoot .32 caliber stuff though.
Be sure to clean the Kulak’s neck hairs off the front sight.
Mosins are "infamous"?
C&R guns are neat investments as for a period of time they're plentiful and cheap, then they dry up. Sometimes overnight. It's all just a waiting game. I remember 9 years ago getting CZ-52’s all day long for $90 delivered (I'd buy 5 at a time). Then they dried up and went up considerably. Same thing with the Yugo 59/66 SKS rifles. I recall them for $80 only a handful of years ago.
Right now the ones I'm concentrating on that stand to increase a good bit are the Yugo/Romanian Tokarev’s, CZ-82’s, and Nazi marked P38’s.
Another good C&R investment is any modern style firearm that was made in the 60’s. S&W/Colt/Ruger revolvers and semi-auto’s, etc. They aren't C&R now, but when they cross that 50 year mark they become C&R and then the value goes up overnight as C&R people will often pay a premium on Gunbroker for the novelty of getting a “modern” gun without going through an 01 FFL.