935 jamming on low brass

I own a 935. Bought it brand new 10 years ago. Its always jammed on low brass shells. I recently decided to give the gas chamber on the barrel and magazine a good cleaning. In doing this i discovered that my gun was inpropperly assembled from the factory. Someone on the assembly line had put my seal ring in behind that strong spring behind that screwed cap. Thats not where it goes. Its to be installed in front of the gas piston with bevelled edge in first. Clean spring and chamber real good and lightly oil with gun oil then wipe any excess off before installing. Yes the spring cap is hard to get back on but with a c clamp and some patience its not a problem. I called Mossburg and they told me that the seal ring does not go in the side that the spring is. I also cleaned the magazine really good and lightly oiled it and dry wipped . I took my gun out and shot about a box and this gun has never worked so good. Thats using 3 gr. Shells 1 oz loads which i demolished about five fire ant hills. Now that was fun. So if your 935 jams on low brass just take out the spring and put seal ring where it belongs in front of gas piston and she should do ok.

Pictures would be nice since I can't follow without knowing what parts your talking about.

But glad you got it working!

Its the barrell gas system on the actual barrell. The part that slidrs over the magszine.

I have a couple old military shotguns (Rem 11, and Savage 720) They are patterned off of the Browning A-5 and you can flip the bushing and install it in different places depending on what load you are shooting. I just thought it was an interesting way to compensate for the low brass rounds.

Great to know, will keep this in mind for advice over on the Facebook group. New guys show up there somewhat regularly complaining of cycling issues with low dram shells. I generally just advise them to be sure before they try to go with the least powerful stuff, to put a few dozen super-stout magnum 3" buck or slug rounds through it to loosen things up.