Ivegot one... Using target loads, it works pretty well HOWEVER if you shoot anything else out of it, the tube magazine where the pin goes through it to retain the gas plunger, begins to bulge and jams the slide mechanism. I had several friends that also have the same gun and all of them do the same thing.
S&w discontinued that gun about ten years ago and sold the rights to someone. They don't have parts, and really don't want to be bothered.
I filed a slight relief in the slide ring and just hammer the tube back into shape everytime it jams. I still use it as a backup gun for deer but use it as a "single shot" therefore I don't count on having a second chance. (don't usually need one)
It is a nice gun, handles well and isn't too heavy to lug around. If I ever find a good machineist, I'll have him make a stronger tube.
To find out if yours is doing this, just slide the ring up and down the magazine tube... if it binds at the end of the piston slot, its starting to bulge.