As for the actual rifle models of Nagant (as they are commonly called) I will not go into them all here, it would require pages and pages. I will discuss one of them though, not as to details of its history but as to its current availability and shootabilty.
Currently there are at least a few online vendors who offer the Mosin Nagant model 91/30. They are usually available with the round receiver but some also come with a hexagonal receiver. Both are usually inexpensive, that is unless you find a sniper model. The regular ones, with the straight bolt handle (it sticks straight out to the side and is not curved down when the bolt is closed) can be had for as little as about $80 plus shipping; figure about $20 to $25 for shipping. Not a bad deal. The sniper rifles, on the other hand go for about $400 to $500 apiece, plus shipping. The biggest difference between the two of them, of which I am aware, is that the sniper rifles have a turned down bolt handle. That means when the bolt is closed the bolt handle is pointing down, and when it is open the handle does not stick straight up as does the straight bolt handle but cants off to the right. The allows for a scope to be fit above the receiver, something impossible to do practically on the straight handled models because with it sticking straight up it gets in the way of scope rail and scope placement on the receiver. Another difference, of course, is that the sniper rifles come with a scope too, some with the original old scopes, some with new replacements.
If I wanted one of these rifles I would not care all that much about whether it had been a sniper rifle or not. I like to shoot em for fun, I am not about to use an old warhorse like a Nagant as a sniper rifle today. I would rather opt for a modern bolt action rifle, in a manageable weight, that shoots .308 ammunition, and that has an adjustable trigger. Yet, when I recently heard that Nagants maybe available with the turned down bolt for only $155 I figured I had best look into the situation. So I did a bit of Internet surfing and came up with this source of the Nagants with a turned down bolt at a great price: RGuns.net. Folks they have the Mosin Nagant 91/30 with turned down bolt for the amazing price of $155. My guess is that they had some extra bolts from the sniper rifles and put them into a regular 91/30.That is just my guess, maybe they were actually manufactured with these bolts but somehow I doubt the price would then be so low.
As for the basic Nagant design - it was built to last. These were true warhorse type guns: big, heavy, strong. They fire 7.62x54R ammunition which is readily available either in surplus (much of which uses corrosive primers) or current commercial manufacture (all of which should be noncorrosive). If you are familiar with them, you don't need me to make up your mind for you. If you are not familiar with them and are a shooting enthusiast, might I suggest maybe you should look into acquiring one or more of them. I am about to do likewise. If they still have them in stock, I will be sending them a copy of my C&R license as soon as possible. Once they receive it, I'll place an order. of course if you have a C&R you can order this rifle directly from them; otherwise you will need to go through a local FFL holder in your area. That adds more to the overall price of the rifle (probably around $50 average across the USA), but the rifle is still worth it in my opinion. It can last you for decades if cared for properly.
For more info on these rifles, see:
All the best and safe shooting,