Moss 590
I am more familiar with Moss 500 but I believe same construction. The Magazine Tube is threaded, as has a thread sealant. A little heat...like from a Hair Dryer or VERY carefully from Propane torch and you should be able to unscrew it. Use either a coated pair of pliers, or a little piece of leather and parrot nose pliers. Be careful not to crush tube.
Problem may be a "burr" on follower or dirt/junk inside of magazine tube. Clean everything, use a dry lube with silicon inside tube and use a reasonable anti-lock on threads when re-installing (lock-tite makes a anti-vibration sealant, do not use Red-Locktite...please).
waltn
FFL, Gunsmithy