930 JM Pro Forearm won't go back on, something tweaked?

[Josh Smith1]

I have a brand new 930 with maybe 200rds through it. I took it apart to clean it but when I went to put it back together, i couldn't get the tube extension on with.

I saw that the forearm wasn't seated all the way because of this piece being rotated somehow. It won't allow the notches to line up. I have no idea how I did this or how to fix it. The dang thing won't budge.

 

[Josh Smith1]

 

[OR3GUN]

Those notches don't need to line up with anything. Of the seven 930s in the shop, not a one has those notches on the same plane. Whatever you do, don't attempt to unscrew that piece as it is under a great deal of pressure by an internal spring and will not easily go back together after you return from the hospital. The notches you see are used for assembling the secondary gas system with a specialized tool. Here is a video you need to watch before doing anything else:

https://www.youtube.com/watch?v=QfqdygODl9k

If that assembly has started to unscrew itself you will need to get it tightened back up before running the gun again. It sounds like either your secondary gas system's ring has worked loose from the groove it belongs in or the assembly itself has started to back out. If it is backing out, a steel tool for replacing forearms on a Mossberg pump shotgun will work to tighten it. The plastic ones Magpul includes in their forearms won't usually hold up to the torque needed to tighten that assembly.

Do you have a side view picture of that assembly? The entire gas system less forearm will make it easy to diagnose what you have going on.

 

[Burk Cornelius]

I knew William would chime in as our resident 930 expert

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[Josh Smith1]

***Follow Up***

Just needed a lil finesse, it was a long day and it was the first time I've worked on this gun.

Thanks fellas

 

[Burk Cornelius]

***Follow Up***

Just needed a lil finesse, it was a long day and it was the first time I've worked on this gun.

Thanks fellas

Bigger hammer?

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[Josh Smith1]

Bigger hammer?

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Nah more wiggle, I was afraid to force it being a new gun an all and the 1st time I've worked on one of these.

 

[Tuflehundon]

I can be tricky until you get used to it. Couple of suggestions that will save you tons of possible headaches in the future.

1. Round off the front of the shell stop. It will keep you from having the "feed from the tube issues" that can pop up with these guns. Brownells has a very good walk through on it. Doesn't happen to all of the guns, maybe 10%, but even if you don't ever have the issue, it will still help the gun feed smoother.

http://www.brownells.com/.aspx/lid=15831/GunTechdetail/Fixing-A-Mossberg-930-Feed-From-The-Tube-Problem

2. Take the recoil spring and recoil spring plunger out of the stock, and grind the front edge of the spring flat. The steel spring can dig into the aluminum plunger and cause burrs on the back side. Did it with my 930 at about 3000 rounds. This catches on the sides of the tube, and slows down the action of the gun. Grinding it flat makes sure it never happens in the first place. You could also get the OR3GUN recoil plunger which captures the spring as well.

http://or3gun.com/OR3GUN/about_or3gun_plunger.htm

If you haven't looked at OR3GUn yet, take a look. They sell tons of go faster parts for the 930's.

 

[Josh Smith1]

Thanks for the info!

I had already planned on ordering their comp kit.

 

[Burk Cornelius]

Thanks for the info!

I had already planned on ordering their comp kit.

We have a bunch of them on our prize table for the contingency program

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[Tuflehundon]

Thanks for the info!

I had already planned on ordering their comp kit.

No worries. 95% of all issues I see with 930's, that aren't user error, are caused by those 2 things.