Need help diagnosing issue with my JM 930 (with video)

[Tuflehundon]

I have a Mossberg 930 JM Pro 24" that I have had for about a year and a 1/2. She ran like a champ for 99% of the time I have had her. Recently I have been having a few hickups at matches. Nothing huge, just enough to piss you off. Shot a 3 gun match today and noticed that it just felt sluggish. Got to a stage were there was no movement and had a friend video me using my Iphone with the slo mo video feature, 120 frames per second.

The bolt seems to hesitate at the rear and seems very slow going forward in the video. I'm wondering if maybe it's a recoil spring issue. I haven't done much to the gun. I have opened up the loading port and that's about it. Everything else is cosmetic like extended chokes, and a match saver.

[T3P_Guy]

I would start with pulling the piston apart and making sure that it is clean and slides easily in the barrel ring, I found using a wire wheel is the easiest way to clean that, the inside of the barrel ring and the mag tube.

Next, try removing the lifter from your trigger assembly and make sure that the two ears that attach it to the trigger group are straight and parallel to each other. The ears are quite easy to bend and to end up out of alignment which can cause some weird feed issues.

The other thing to watch is the spring that is under the shell catch (the one behind the back of the catch that is between the catch and the receiver, it can get kicked off to a side which will cause it to feel kind of clicky when you push in the bolt release button when the gun is empty. If this happens you can reach in with a pick and get it straightened out.

[WCK]

It looks like you are having a problem feeding shells from the magazine tube.

You have to take out the carrier latch and polish the shell stop end.

I can't post a link to the fix, I don't have enough posts.

Brownells Gun Tech has a tutorial that Larry Weeks wrote: Fixing a Mossberg 930 feeding from the tube problem.

[Tuflehundon]

Found this when I took the gun completely apart to check everything. It's the recoil spring plunger that goes in the stock and interacts with the tail on the bolt. Had some pretty bad burrs on the outside rear edges of it. This is not the 1st 930 JM Pro my gunsmith friend has seen with this issue. I chucked it into my drill and used a file on it to round the entire rear edge of it. The plunger was difficult to get out of the tube originally. I think it was my issue. It looked like the spring itself did the damage to the plunger. Looked like it had dug into it over time.

I'm gonna go ahead and polish the shell stop end of the carrier latch and a couple of other things while I have it apart anyways just in case. Thanks for the help. I'll report back once I get a chance to put some shells through her later this week.

Edited October 19, 2014 by Tuflehundon

[WCK]

That will definitely slow the bolt speed down.

[Tuflehundon]

Ok, so I shot her today and the bolt was running at the right speed this time, but I am having issue feeding from the magazine. Didn't get a change to polish the carrier latch before testing her out today but will do that now next week. Thanks for that advice, I think that may be the rest of the fix that I need.