My Mossy 500 is still practically brand new having only about 5 boxes of shells through it. I’d noticed that the action on it was a lot stiffer, and had minor “stutters” in it, than my used 835. Rather than wait a few hundred rounds for it to break in I decided to see if I could slick it up a bit.
With the trigger group out of it I noticed that the effort on the slide increased quite a bit as the bolt was clearing the ejection port rearward, and the bolt carrier leading edge tended to hang up just a bit against the rear edge of the receiver rail as it moved forward.
With the gun stripped I started checking each receiver part for burrs. Both the cartridge stop and interruptor had quite a bit of “flash” along the corners which I removed with a jeweler’s file and 220 grit sandpaper. I noticed that the interruptor ramp on the right side action bar had a sharp transition at the top so I rounded that off and smoothed it out.
The largest improvements came from the rear of the shell lifter and massaging the bolt carrier slightly. There was quite a bit of flash on the inner edges at the rear of the shell lifter and with that removed the rearward travel of the bolt is much smoother. On the leading edge of the bolt carrier I radiused those sharp edges there (about 1/64") with the file and sandpaper, and sanded the underside of the carrier where it slides in the receiver rails.
While not as slick as my wife’s 870 Remington these minor bits of work seriously smoothed out my Mossy. There is, however, one minor hiccup that can’t be cured. The ejector catches in the bolt slot because the extractor pin hole just intrudes into the slot. You’d probably never notice that when racking the slide but it is very apparent when sliding the bolt inside the receiver by hand.
With the trigger group out of it I noticed that the effort on the slide increased quite a bit as the bolt was clearing the ejection port rearward, and the bolt carrier leading edge tended to hang up just a bit against the rear edge of the receiver rail as it moved forward.
With the gun stripped I started checking each receiver part for burrs. Both the cartridge stop and interruptor had quite a bit of “flash” along the corners which I removed with a jeweler’s file and 220 grit sandpaper. I noticed that the interruptor ramp on the right side action bar had a sharp transition at the top so I rounded that off and smoothed it out.
The largest improvements came from the rear of the shell lifter and massaging the bolt carrier slightly. There was quite a bit of flash on the inner edges at the rear of the shell lifter and with that removed the rearward travel of the bolt is much smoother. On the leading edge of the bolt carrier I radiused those sharp edges there (about 1/64") with the file and sandpaper, and sanded the underside of the carrier where it slides in the receiver rails.
While not as slick as my wife’s 870 Remington these minor bits of work seriously smoothed out my Mossy. There is, however, one minor hiccup that can’t be cured. The ejector catches in the bolt slot because the extractor pin hole just intrudes into the slot. You’d probably never notice that when racking the slide but it is very apparent when sliding the bolt inside the receiver by hand.
I'd sat there & racked the thing until my arm was ready to fall off without a noticeable change, that's why I went the "tune up" route. I know it'll never be butter smooth like the 870, I just wanted it better than it was and thought a post on my efforts might help out a new Mossy owner.