There is no golden bullet when buying a Mosin. Each one needs to be examined individually as they can run the gambit from like new to trashed and abused. If you want a shooter the way to get a winner is not to start with narrowed expectations of what you want (year of manufacture, arsenal, etc..) Start with the idea that you want to find an excellent example mechanically, because you are as likely to find an amazing shooter from any year, from any arsenal, round or hex receiver.
Mechanically you want to look for matching numbers, a good clean bore that is not counter bored (although this is not always an indication of a bad shooter) and general condition. Pre war (before 1939) overall tends to be better fit and finish. All hex are pre-war and generally are better finish than war time production.
From a collector standpoint, there are tons and tons of things that can make or break the collectability of a Mosin. Ex-snipers, re arseneled versus not, Finn captured, pre-war versus post war stocks and parts, ex-dragoons, scrubbed pre 1917 markings versus not scrubbed, which arsenal (Tula, Chatellerault, Izhevsk, White Westingtonhouse, Sestroryetsk, Remington) and the list goes on and on and on.
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