View Full Version : Mossberg 500 Troubles

July 12, 2012, 09:49 PM
I recently inherited my great-uncle's (and best hunting buddy RIP), Mossberg 500 12 GA. I'd like to take it out a few times this season but I'm having some troubles:

1) I can not get the forearm/bolt to "lock-up" in the forward/fire position unless I really slam it forward. If I do not slam action closed and I stand the gun on end...the action will open on its own.

2) Looking down the sights: the barrel is rotated counter-clockwise a few degrees. Enough to notice and move the bead sights.

3) Stock has a hairline crack at the receiver. Does anyone have any experience with the Boyd's Plainsman stocks? Any pics?

I gave her a pretty good cleaning and got a lot of junk out of it. I inspected the areas where the barrel mates with the receiver and they look clean, no burrs, dents, etc.

The only thing I can think of right now is the magazine tube bent or twisted? How would I be able to tell? What would be the fix?

Thanks in advance! :D

July 12, 2012, 11:40 PM
I'm just going to ask the obvious... Is the barrel on all the way? With no lockup AND off center sights, that's what I'm thinkin is it might be hung up on the inside by a few thousandths?

I guess another question- were the sights always like that? Did you shoot it any time before?

July 13, 2012, 12:51 AM
I'm just going to ask the obvious... Is the barrel on all the way? With no lockup AND off center sights, that's what I'm thinkin is it might be hung up on the inside by a few thousandths?

I guess another question- were the sights always like that? Did you shoot it any time before?

Thanks for the suggestion.

I just tried 2 other barrels and they all have the same issue. I tightened them as far as I could. It looks like they are all making contact inside the action. One has a vent rib and the rib is definitely off center from the receiver by a fraction of an inch. I took 4 pictures, are these gaps within spec/tolerance? It's been awhile since I've looked closely at a 500.

Album: http://imgur.com/a/OM5IA#0

I've seen him shoot it but I never have until it was passed to me and I ran a few rounds through it fine. I think this is something he would live with or work around.

July 13, 2012, 02:22 AM
It soesn't look as though the barrel is fastened down all the way. See the gap between the lug and the end of the magazine. Why?

Does the magazine tube screw into the receiver on a Mossberg? If it is removed, do the barrels line up with the receiver? If it is supposed to unscrew, but is in really tight, you may want to take it to a smith rather than risk damaging the magazine. If it is tweaked, does it have to be replaced or can a good smith straigten it?

the rifleer
July 13, 2012, 03:14 AM
When you put the barrels on, do you open the bolt half way? It has to be open half way, it can't be closed or opened all the way or else it won't go on all the way, although that doesn't seem to be the issue because of how far you have it on.

July 13, 2012, 07:41 AM
I'll address the crack issue- if it isn't too bad, it should be able to be repaired with a good glue. I cracked a Browning O/U through the wrist and my gunsmith (who is also a stock man), used some uber-glue and pins to repair it - the stock break is hardly noticeable and is stronger than ever. You might need to use a hypo needle to get the glue in there with some good clamps, but it might work

From your pics, it appears that something is not allowing the barrel to fully seat - it should not look that way

July 13, 2012, 08:18 AM
To take Oneounceload's stock suggestion a little further (I'm a wanna-be woodworker). Get the slow-setting type of superglue. Remove the stock from the receiver and see if you can temporarily open then crack. Frequently a wedge (used on the receiver end so it won't mar anything) can open it up a little. Flood the crack with superglue and used a VERY gentle blast of compressed air to force the glue down into the crack. Work quickly to avoid glue setup and get glue into every place in the crack you can. Remove the wedge and clamp the stock (if using a metal clamp, use some protection for the wood). Wipe the glue squeeze out with acetone before it sets.

July 13, 2012, 12:17 PM
Your barrel rotation:
The front of the ejector has a protrusion that sits in the notch of the barrel extension. If this protrusion is broken off it will allow the barrel to rotate. If not broken, the barrel extention notch or the ejector needs adjustment or replacement. You ejector could also be missing altogether.

With the action open look in through the ejector port. You should see a screw head on the opposite side. Forward of that screw is the ejector protrusion. If you loosen the barrel and pull it out and reset it you will see the alignment of that tab into the barrel notch. If no screw is present (part #26) or you don't see metal piece under it that the screw should be holding in (part #27) you are missing the ejector.

The breech lock up problem is most likely caused by the clocked barrel. The Bolt Lock (Part #29) is not able to engage the barrel due to early contact on the right side of the barrel locking extension (The big square notch in the back of the barrel). If you pull the bolt out and look at that part (you can push it up manually)at the right side you will probably see a shiny area along the length of it. You should also see wear on that part of the barrel that you don't see on the other side.

The amount of gap in your picture between the barrel end and magazine tube is about normal. It looks like someone in the past pulled the mag. tube off by the look of the scratches near the end. God only knows how much they torqued it back in. You can not put the barrel on with the slide all the way forward or all the way back.

Schematic to refer to: Numrich (http://www.gunpartscorp.com/catalog/Products.aspx?catid=11934)

July 13, 2012, 01:07 PM
I do a lot of woodworking...and stock repair is not a great place for super-glue...( cyanoacrylate glues ) harden pretty quickly / and tend to be brittle, in my opinion.

If you're going to try CA glue....then try this brand in the Yellow bottle...its a gap filling formula - bonds in 10-25 sec...but I would not use an accelerator on it ( or it'll be even more brittle when it dries).



the green formula is a little heavier viscosity ...and will bond in about 60 sec.
I've tried a lot of different brands of CA glue...and this one is by far the best in my view. I use the yellow formula quite a bit on "wood turning" projects where I need to glue a brass sleeve into a wood blank, etc...
But for a stock repair, I would personally use a water resistant - yellow woodworkers glue ...like TiteBond II . I think it'll give you a stronger joint.

Depending on where the crack is ...you might need some dowels/pins ...but an experienced woodworker can hide the fastener pretty well / and then refinish the stock. I make my own "wood putty" ...by mixing the sanding dust from a particular species of wood..and mix it with some glue ..until I get the right consistency ...and since its the same species, it'll really hide any joint crack very well - and it'll accept the stain or finish better than any commercial product usually.

July 13, 2012, 04:44 PM
Jim does much more woodworking than me, but what about Titebond III. Titebond bills it as the "uitimate glue". Clamping time is 30 minutes; avoid dress for 24 hours.

July 13, 2012, 05:02 PM
Easier still, just buy a replacement....wood or synthetic they're easy enough to get and fairly inexpensive. A factory replacement synthetic butt stock is $55 at Midway.