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Mossberg 500 Mainspring Retaining Pin walking out

S

Stanislao

.22LR
When I purchased my 1999 Mossberg 500 I found it extremely difficult to remove the trigger group. This, I found, was because the mainspring retaining pin had moved from it's hole and was catching on the stock. Pushing the pin back into place resolved the issue. Until Sunday's four rounds of clays, that is. Same issue, same fix.

While the pin is not symmetrical, this is in keeping with other Mossberg 500's I've seen, and the pin does not appear damaged. Mossberg customer support recommended sending the trigger group in, which I suspect would end up with me being charged for a new trigger group. What's going on with this thing, and how do I fix it?
 
Mossberg-500-trigger-assembly-diagram.png

#39 is the pin in question.
 
Stanislao said:
the pin is not symmetrical
Click to expand...

Yes, the pin is flared at one end. This is what holds the pin in place, or supposed to.

It is possible that one side of your trigger housing is wallored out from this flaring. You may be able to spin the pin around, put it in the other way and get it to stay.

Retaining compound will also help, it is threadlocker for pressed components. If that doesn't work get out the epoxy :mad:
 
Since we're on the subject.

Mossberg uses a flared/serrated type pin. These pins are used at the back of the trigger group, firing pin and each extractor. These pins are similar to staking in that they are a method to mechanically lock components. Unlike staking the flared pins are much easier to install and are reusable.

The bolt pins pretty much only go in one way. With the trigger it is quite possible to knock it all the way thru either end. If the flare is driven all the way thru the housing it will be a PITA and risk walloring out. With these pins remember that the flared side is 'first out, last in'. The mainspring pin can be installed from either direction from the factory; it is best to follow this direction for each gun.

Retaining compound can be used to secure these pins although it is typically not needed. In OPs case I think the best bet is to install the pin from the opposite direction, therefore giving it a 'fresh bite'.

Large hammer spring pin on left, firing pin-pin on right.
 
"Where... a bearing is secured by a press fit the actual metal-to-metal contact accounts for as little as 30 per cent of the total surface of the joint.

...tests have shown that the axial strength of an interference fit component can be increased threefold by introducing an adhesive to the joint.

The adhesive can be used on its own or in combination with mechanical methods. [i.e. get both]"

Full Article Here
 
Personally I would not recommend using an adhesive there nor would I recommend reversing the pin and installing it from the other direction.

Guns get hot and most adhesives lose strength when they get hot. That's how you remove Loctite: get it hot!

If you have epoxy on a metal gun, and you set it in the hot sun, and that gun gets good and hot, the epoxy will weaken noticeably. You will be able to tell just by poking it with your fingernail.

And at just 250 degrees you can lose 50% of the strength. It actually typically starts weakening about 125 degrees. It's even worse if it's wet.

Steel-filled epoxies are stronger and lose strength slower, but they can rust. I'm not saying it won't work I just think it's a bad practice personally.

When you reverse a flared pin in a gun all you do is wallow out the smaller hole, plus you've put the small end of the pin in the loose hole

What the hell good is that?

The thing to do is to enlarge the large end of the pin. If it's already grooved, put a chisel in that groove and tap it with a hammer to flare the pin a bit more. If it doesn't have a groove, you can groove it, but you don't need to.

You just have to make the flared end more oblate. Figure out which is the flatter dimension and tap it there with a hammer to make it slightly flatter. The pin will expand in the opposite direction and now it will fit in the hole.

Some pins have a tiny knurl, and you can just take a little hammer and chisel and you can improve the impressions of the knurl until it fits nicely. Use a hardwood block or a soft aluminum block as a backup so you just don't flatten out the opposite knurl.
 
It'
CaddmannQ said:
Personally I would not recommend using an adhesive there nor would I recommend reversing the pin and installing it from the other direction.

Guns get hot and most adhesives lose strength when they get hot. That's how you remove Loctite: get it hot!

If you have epoxy on a metal gun, and you set it in the hot sun, and that gun gets good and hot, the epoxy will weaken noticeably. You will be able to tell just by poking it with your fingernail.

And at just 250 degrees you can lose 50% of the strength. It actually typically starts weakening about 125 degrees. It's even worse if it's wet.

Steel-filled epoxies are stronger and lose strength slower, but they can rust. I'm not saying it won't work I just think it's a bad practice personally.
Click to expand...

It's not like it's a load bearing part, Cadd. It's a pin that gradually backs out a hair. A dot of fingernail polish or a dot of tung oil/varnish will keep it in. My guns, however, the wood of the stock keeps the pin in place. Not sure how his is backing out. And enlarging the hole weakens that hole....and that hole IS a load bearing part.
 
Richard I'm sorry. I don't mean to sound like one of these internet Wise Guys.

I realize it's a minor deal, and I don't mean to blow it out of proportion. I just think things like Loctite and JB Weld are sort of a last resort, and so of course I'm going to continue to rant on the subject. :rolleyes:

This prejudice probably comes from the engineering business. On practically every project that we did, there were mislocated anchor bolts or bent or broken anchor bolts, and of course the contractors solution was never to dig up the concrete and do it over. It was always to put in an epoxy bolt.

On paper an epoxy bolt looks good enough. But there is no way on God's Earth that it is just as good.

Because epoxy weakens under heat you are never allowed to suspend things overhead from an epoxy bolt in tension.

Anyhow these things do have their place, but where metal-to-metal contact is needed it is best to have it.

Right now I'm working on my fiberglass boat and I have put a lot of epoxy and plastic resin into it. I don't hate this stuff. In fact it's a miracle of science that it exists.
 
Not at all, bud. I enjoy your posts. Keep sounding exactly like you have. Just that that pin in the trigger group takes zero stress in the direction that epoxy/JB Weld etc would matter. It's not in tension. The adhesive is simply to keep it in the sideways hole. No stress at all really except the possible slight slope of the staked end working its way out. But that HOLE, that's in a stressed position. That mainspring puts quite a bit of force on that hole and widening it in any direction is one more stress vector that can break that hole.
 
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Are we talking about guns with a plastic trigger group or a metal trigger group? I don't know the history of these things...
 
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