Reddit mentions of The Mosin-Nagant Rifle, 6th Edition (For collectors only)

NO EXCEPTIONS

Much better. But you really need to be more focused. Start with this book that will give you a good general survey of the field you have mentioned:

https://www.amazon.com/Military-Full-Color-Favorite-Vintage-Surplus/dp/1931464391

Then move into something a little more specific and in-depth like this:

https://www.amazon.com/Magazine-Loading-Rifles-revised-Paperback/dp/B00QD9QWBS

or this:

https://www.amazon.com/Backbone-Wehrmacht-German-Rifle-1934-1945/dp/B000KK29O0

or this:

https://www.amazon.com/Mosin-Nagant-Rifle-6th-collectors-only/dp/1882391217

Part of the reason to focus is that it's difficult to know any level of detail over such a broad range. It takes a LOT of time and effort.

Also go check out Othais https://www.patreon.com/CandRsenal and throw him some dollhairs every month. His content is FANTASTIC!

Finally use the interwebs...

http://www.swissrifles.com/
http://www.k98kforum.com/forum.php
http://7.62x54r.net/

And as others have mentioned you need to start developing a keen eye and sense of "correctness".

• Is it refinished?
  
• Is the stock refinished? Sanded?
  
• Has it been bubba'd in any way? Barrel length, stocks, sights added, etc.
  
• What are the ideal characteristics for this gun? Matching #s or "correct?
  
  You need to see guns in person to develop this to the point where you can start picking things out in photos.

Welcome aboard comrade. I would recommend picking up a copy of this: http://www.amazon.com/Mosin-Nagant-Rifle-5th-collectors-only/dp/1882391217/ref=sr_1_1?ie=UTF8&qid=1322758056&sr=8-1. You can probably find an older edition for less used maybe. Mine has served me well and is saturated with solvent, oil, and cosmo :D. There is an extensive amount of data about markings, both original russian and those used by common adaptations by other countries.

Also, if you shoot that military surplus ammo that you can find super cheap, make sure you clean your rifle afterwards. It is berdan primed and attracts water and can cause rusting if not cleaned after shooting.

Ok then, military surplus rifles. That's a solid place to start. Here's a rundown:

I actually don't have a K31 book, but this one is written by Joe Poyer who is an author I trust. K31s are pretty straightforward for the most part, it's the earlier rifles that are a tad complicated to study.

There's so many damn Mausers that it's hard to recommend a book that covers enough of them. This one should be enough to get you started. This one just came back in print and is for the Swedish Mauser.

For Mosins, This one should provide enough knowledge, but there's actually a surprising amount of material online. Not many printed books on Mosins in English, sadly.

For Enfields, Ian Skennerton's book is the go-to.

And that should be enough to get you started. For any other guns, just type the gun name followed by "book" into Google and you should find what you need. And as always, the internet has plenty of it's own resources too.

Heck, if you're a history junky, the best book available on the subject that I am aware of is The Mosin-Nagant Rifle by Terence Lapin. There is an amazing amount of info on the internet too, of course. It is interesting to me that most modern bolt action rifles descended from just a few that were designed right around 1900 -- the Mosin Nagant 1891 being one of them. I honestly was not aware of that until recently when I started reading up on the history of them myself. Good stuff!