The M39 was the end of a cumulative series of new models. The government decided that producing several models was a total PITA, and they hammered the models into a cumulation of features during the 30s. The result was the M39.
That's a quick and dirty history from mosinnagant.net. Go
there to read about the history.
The M39 is much more than a reworked M91/30. a reworked 91/30 would be a
Finnish 19/30.
The
M39 was often made with recycled parts and receivers, however. Most Finnish Mosins I've seen have Russian/Soviet receivers, and many have foreign made barrels. Small parts are commonly of the "parts bin" variety. For example, my 1945 M39 is built on a 1910 Tula receiver and has a Pre-1928 Izhevsk bolt group. It shoots into 2 MOA with Czech surplus and sometimes into 1.5 MOA. The M39 is worth at least double what they sell for, IMO.
You can buy a good condish wartime starter (and it WILL be a starter. these take over your life.) M39 by trolling the used market for good deals. The EE on gunboards.com and surplusrifle.com have them, as do the auction sites.
Right now one of the best deals going on (besides the ones on my Christmas list
) is from
empire arms. They have good to VG wartime M39s as low as $200.