[Dr.Tramp]

I bought a used 930 8 shot Tactical shotgun from a guy for the grandson and with the right ammo, high velocity stuff, it works perfectly.
But when I took it apart to clean it the mag spring seemed to be very long compared to what I'd seen in various disassembly-assembly videos and the coils were unevenly spaced so I figure the previous owner had stretched it to try and get more pressure on the shells in the chamber. Why? No idea but getting it back into the mag tube is a PIA.
So I ordered a new spring from Mossberg, PN# 18450, and it is at least a foot shorter than the old spring and as soon as the grandson gets time to come over we're going to swap the springs and see how or if it affects the feeding.
Ride Safe. Dr.Tramp..............

 

[Flash]

Keep us posted. I'm curious.

 

[Dr.Tramp]

Will do.
Ride Safe. Dr.Tramp................

 

[Blackmesa96]

Bought a 930 (tactical, 18.5" barrel) new, and the mag spring resembled one of those snakes in a can first time I took it apart. It sure seemed longer than I thought it needed to be.

Reassembly is definitely a pain, but much like my P938, it gets easier once you do it a few times. I found that using one hand as a funnel/chute of sorts helps getting the snake back into the can.

While I wouldn't rule out someone having stretched the spring, don't know why someone would think it solves cycling issues. Like you said, it runs well if you use higher velocity shells.

Some of these guns have a seal on the piston, others don't. You can contact Mossberg customer service with your serial number they can tell you if yours is supposed to have one. If cycling is problematic, replacement may help. That could be a reason someone decided to try to create more spring pressure.

You probably know to make sure all the gas system is clean. If you stay away from target or reduced recoil loads, it should run like a champ.

 

[Dr.Tramp]

I replaced the old spring today and while it was longer than the new one, 2-3 inches, it wasn't as stretched as I thought. Next step, take it to the range and see how it feeds.