Mossberg 930 Tactical Shotgun Review
Part 7 - Shimming Loose Trigger Housing
March 29, 2013

Mossberg 930 Tactical Review Shimming Trigger Housing

During my review of the Mossberg 930 Tactical Shotgun, I noticed that the trigger housing was loose and this seemed to prevent the shotgun from easily switching from "safe" to "fire" if upward pressure was applied to the trigger housing.  I sent the shotgun back to Mossberg, but they made no change to the looseness of the housing.  After taking a close look at the receiver and trigger housing, I decided I could easily shim the housing.  Before I go any further, I want to be clear that any time you decide to work on your firearms, you are taking on your own liability and risks along with potentially voiding your warranty.  The instructions shown in this review document what I did to remove the looseness on my shotgun and are not formal instructions endorsed by Mossberg.

Before I tried any shimming, I first confirmed that the shotgun safety would function properly if the trigger housing was shimmed away from the receiver.  To do this, I pulled down on the housing using the trigger guard and verified the safety would function properly and the shotgun would not fire with the safety in the "safe" position.

 


Temporary Shim

My first step was to create a temporary shim to checkout how the shotgun would perform with all the freeplay shimmed out of the trigger housing at the rear end of the housing.  The area I wanted to apply the shim was at the shelf at the rear of the receiver.   You can see this shelf identified in the photo below.

Figure 1
Mossberg 930 Tactical Review Shimming Trigger Housing

The shim would then bear against the rear of the trigger housing shown below.

Figure 2
Mossberg 930 Tactical Review Shimming Trigger Housing

For my temporary shim, I rolled up some painters tape (sticky side out) until it made a cylinder about 1/8" in diameter.  I then placed this cylinder of tape on the shelf shown below.  I made sure the cylinder was also pressed against the back of the receiver.  I installed the front pin on the trigger housing and then rotated the housing into place.  The housing required a little pressure to deform the cylinder of tape flat enough so I could install the rear trigger housing pin.  The photo below actually shows how the tape was deformed after I removed the trigger housing.

Figure 3
Mossberg 930 Tactical Review Shimming Trigger Housing

With the trigger housing installed, it was hard to detect that a temporary shim was in place.  This method removed all the the looseness of the trigger housing and I actually consider this could be a long term fix.  After further pondering, lubricants would probably breakdown the tape and I didn't think this was really the best option long term.  I range tested the shotgun and it functioned great.  No looseness and the safety worked perfectly.

Figure 4
Mossberg 930 Tactical Review Shimming Trigger Housing

The photo below shows the tape removed.  You can see that the tape shimmed both in the vertical, forward/rear and lateral directions.  This would be what I would want on a long term (permanent) shim.

Figure 5
Mossberg 930 Tactical Review Shimming Trigger Housing


Permanent Shim

For my permanent shim, I decided to use some Devcon Plastic Steel Epoxy that I have used as bedding compound in the past.

Figure 6
Mossberg 930 Tactical Review Shimming Trigger Housing

I cleaned the area with Xylene (other types of solvent would also work).  I used the Xylene because it seems to be better at cleaning up epoxy compounds.

Figure 7
Mossberg 930 Tactical Review Shimming Trigger Housing

Next I put two coats of automotive Turtle Paste Wax on the rear of my trigger housing in the area that would contact the Devcon.  My goal was to make the epoxy shim stick to the receiver and not the trigger housing.

Figure 8
Mossberg 930 Tactical Review Shimming Trigger Housing

I added layers of tape over the end of the safety plate so that when I installed the trigger housing, the safety plate and tape would keep the trigger housing pushed as far down as possible.  Note that the safety must be in the "safe" position during this shimming effort.  I kept adding layers of tape over the end of the safety plate until I felt that the trigger housing required a little pressure to push the trigger housing in place and install the rear pin.  In my case, I added  4 layers of tape.  I missed getting the photo in the correct sequence, so the photo below shows the tape over the safety plate and the shim is already installed.

Figure 9
Mossberg 930 Tactical Review Shimming Trigger Housing

The photo below shows how you can install the front pin on the trigger housing and rotate the housing into the receiver to install the rear pin.  I used this method to get the layers of tape to the correct thickness.  I also used this method to rotate the trigger housing in place after applying the epoxy.

Figure 10
Mossberg 930 Tactical Review Shimming Trigger Housing

These next two photos show my finished epoxy shim.  You can see how the trigger housing formed flat surfaces at the rear and above the shelf on the receiver.  Also, notice that there are small curved corners where I was able to get some of the epoxy shim to support the sides of the trigger housing.  I wish had put a little more epoxy in the corners so that the portion that squeezed out (and I cleaned up) would have made a nice curve to match that of the bottom of the receiver.

Figure 11
Mossberg 930 Tactical Review Shimming Trigger Housing

When I removed the trigger housing for the first time, the wax didn't let any of the epoxy stick to the housing and the housing came out easily.  Overall, I was very happy with the shimming results.  There is no looseness with my trigger housing and the safety works perfectly regardless of how much pressure you put on the trigger housing.  A key point here is that after you do anything with your firearms, you should always make sure your safety features work properly.

Figure 12
Mossberg 930 Tactical Review Shimming Trigger Housing

The photo below shows the shotgun with the trigger housing installed.  Like I mentioned, I think a little more epoxy in the corners would have made a nicer looking shim, but I'm still pleased with the results.

Figure 13
Mossberg 930 Tactical Review Shimming Trigger Housing

 

Thoughts

Shimming was actually a very simple fix for something that would have nagged at me for years.  As I shoot the shotgun over the next months/years, I will keep an eye on this shim and update this part of the review if things change.

For more detailed photos and commentary, make sure you check out the other parts of this review and feel free to leave comments on my Reader's Comments page.  The following links are provided to help you see other parts of this review. 


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