Double feed, fail to feed, fail to extract, or fail to eject?
The spring in the tube in the stock is the inner magazine tube. It is highly likely that there is nothing wrong with the spring, but that the guts of the rifle are filthy. I have a few Mossbergs (Heh heh heh) including 51Ms and 151Ks that use the same action as yours. When the bolt comes back, it trips a little wire clip that allows the inner mag to SPROIT one catridge straight into the chamber. However, the buildup of carbon and the waxy lube from 22 ammo can gunk it all up. All of mine were fairly cruddy when I got them.
I would begin buy pulling the action (take pictures as you go) strip it, clean it GOOD, light lube, then pull the inner and outer mag tubes, clean those on the inside (gunscrubber spray, rod them out) pay attention to how that little wire clip and the U shaped catridge release are fitted before you remove them. Be sure to scrub the chamber area properly.
PS- Is NOT the nature of the model. All of mine will empty a mag as fast as you can twitch a finger.