I had the SPR-310 o/u, and currently have the SPR-453 3 1/2" auto. For the money, the SPR-310 is a decent gun. It has mechanical triggers and selective ejectors/extractors, and with a little TLC, was one of the best shotguns I have owned. At first I had the same problem Grimjim mentioned, and I took mine apart and cleaned the innards thoroughly and got all kinds of wood and metal shavings out of it. They are built in Russia from good steel, but the fit and finish leaves something to be desired, and the lubricants used at the factory are way below par. I polished some of the moving parts, replaced the ejector springs with lighter springs, disabled the auto safety engagement, and lubed it up with quality lubes. Afterwards, it functioned better than the 525 Sporting Grade 1 I bought to replace it. Two Brownings (525, and Citori Special Sporting Clays) and the SPR went down the road, and the one I miss the most was the SPR. I'm sure I'll get some flames from my comments, but anyone who has shot with me in the winter here in WI will not be among them. The guns speak for themselves. My Beretta Silver Pigeon was as dependable as my SPR-310, but neither fit me well.
The SPR-453 was an informed descision. Upon recieving it, I took it down to clean and polish the innards, only to find everything as smooth as on my trusty A390. Sometimes you get lucky I guess! I squirted it with rem-oil, and began my own reliability test. I'm over 600 rounds without even cleaning, everything from 3 1/2" mags down to 1 oz. 2 3/4" reloads. It has yet to have a failure of any kind.
There is a forum dedicated to the Baikal/Spartan here:
http://www.shotgunworld.com/bbs/viewforum.php?f=83&sid=1abe01086377b77c5f8d0dd1d094d629