Help Repairing Mossberg 500 Shotgun

[abbyonheyward]

Hoping to tap into the knowledge and experience of the members.

I bought a used, nickel Mossberg 500 ATP pistol grip shotgun about 30 years ago. 12 gauge pump with dual action bars.

At some point, the pin that holds the right side action bar in the action tube fell out and got lost. The action bar fell out, too. Fortunately, I managed to hold on to the action bar.

I’m now trying to re-install the action bar with hopes of it not falling out again.

Unless I am mistaken, each action bar is pinned to the action tube with a separate pin (i.e. two pins, total - one for the right side action bar and one for the left side action bar). It does not appear that there is a single (long) pin that holds both action bars to the action tube that may have sheared off on the right side.

Cursory Google searches, searches at the Mossberg Forum and YouTube reveal lots of information about replacing forends and the action tubes, but I am yet to find anything related to the action bar and the pin that affixes the action bar to the action tube.

In summary, it appears that the pin in question is 3/32” in diameter and approximately 1/4” to 3/8” long.

I can’t figure out what, if anything other than friction, holds the pin in the action tube. I am confident that the hole and pin are not threaded.

I appears that the hole for the pin isn’t tapered. Would the pin itself be tapered in order to ensure a tight fit when it is pressed or hammered in?

I am concerned that if I simply insert a straight 3/32” pin in the existing hole, it will probably fall out relatively quickly. If possible, I would like to avoid using any type of adhesive to hold the new pin in.

In the attached photos, you can see the intact left side action bar that is held securely in place by a pin. You can also see the unattached right side action bar and the hole for the pin.

I know Mossberg made millions of these shotguns, but it seems like a poor design for moving parts (action bar and action tube) that are subject the force of cycling the action and recoil.

I know that at least one of the major gun part vendors sells the action bars, but the parts diagrams do not show the pin(s) that affix the action bars to the action tube.

Any ideas on how to securely pin the action bar to the action tube? Any ideas on what the pin should look like and where to source one?

Thanks, in advance, for any assistance you may be able to provide.

Ryon

 

[Justin T]

Pins like these are not effective if they are exactly the same diameter as the hole they are supposed to go in. They are supposed to be fractional thousandths larger than the holes so that they have an interference fit. They shouldn’t go in with just finger pressure alone.

If I were you, I’d be hunting down a couple of spring roll pins slightly larger than whatever drill bit measurement you are using, and some blue loctite at Lowes or Home Depot, and rolling with that.

I’m betting that hole where those pins go is a thru-hole. Can you see light thru it? If so, then you don’t have to be super-rigid about finding a pin with that exact length.

If it’s not a thru hole, you can measure it by dropping a toothpick in the hole and marking the toothpick to get a more exact length.

 

[Protocall_Design]

Look for a 3/32 spirol pin or coiled spring pin at McMaster-Carr. Get the longest length that will comfortably fit. Drive it in with a hammer. It will be an easy press fit. Done.

 

[abbyonheyward]

Great information. Thanks for the guidance. I really appreciate it.

 

[2152hq]

Usually there's a forend that slides over the metal tube and then over the rear junction where the op-rods are pinned in place. The forend is secured by a ring screwed into the tube at the front (threaded) so it stays in place.

The forend covering the 'pins' captures them from falling free of the assembly.
The pins are supposed to be a slip fit as they are a blind hole.
You would have no way of (easily)removing them if the need to replace one or both of the op-rods should occur if the pin(s) were a force fit.
If the pins were meant to just hang out there in the open, they probably would have used a screw assembly instead.

The pins don't actually take any of the brute fore of operating and shucking the action open and closed, they just hold the oprods in position.
The squared cutout on that end of the rods mates over a lug on the forend. That locks the op-rod into position and takes the abuse.

That's what I remember of the 500 but it's been many years since I worked on one. Maybe I've got it all wrong.

 

[Drm50]

I’ve had dozens of Moss pumps apart but never had occasion to mess with action bars. Swap out for ends it isn’t required. That pin is very low tech piece. Cut a drill bit shank proper length and drop in with shot of thread loc and forearm will keep it from falling out.