Mossberg 500a problems...

[Third_Rail]

Doublefeeds, jammed action, etc. This is a 1962 to 1968 (don't know exactly) Mossberg 500a with the single action bar. This NEVER happened to me before, and I put 15 rounds through it without a hitch (I know, that's not much)


Today I went to the range (yesterday, I know... ) and Jrob24 and my fiance both experienced double feeds and an action jammed so tight that I had to take the barrel off and hold the forend then smack the butt on the ground. This happened with an empty mag tube, a full one, and five, yes five, brands of ammo... maybe 5 double feeds and twice as many times the action stuck. This in only 100 rounds of ammo! What gives??



A while back the man I bought this from fixed it for me by replacing the bolt assembly with one from a 20ga - the firing pin was broken and he didn't have any more. Could this be the cause, or is it something else?


Also - odd, but firing from the hip eliminated these problems (which I never experienced in the first place, only Jrob24 and my fiance)



If anyone has even a slight idea, please tell me. I need to get this fixed as it's my only firearm and currently my HD firearm.

All I can do for now is leave one in the chamber and hope that if I need another the action doesn't jam.

 

[Third_Rail]

After a thourough cleaning and inspection, I think there are two problems here - one is that the shell stop is bent, significantly. Looks like the previous owner unscrewed the forend with it or something similar! I'll straigten that out and clean the groove it sits in. That'll fix the double feeding, I'd bet.


Any ideas on the jammed action, though? Doesn't do it at home with no ammo feeding, and I don't have any dummies or snapcaps to test it.

 

[Rupestris]

This is a 1962 to 1968

Just a guess, but could the mag spring be tired/worn out?

 

[mattw]

do you know anything about this gun's life before you? from what i hear mossberg used to be pretty crappy stuff back in the day..

 

[Third_Rail]

I don't think a weak magspring would cause the action to jam... though I'll replace it anyway.


This seems ANYTHING but low quality, considering it's probably had hundreds if not thousands of rounds through it over 40 years - probably a lot of bad conditions too (hunting, etc.)


I honestly think that this is something that has happened since I got it.

 

[Rupestris]

Only reason I question the mag spring is that it does not jam when unloaded. The only difference would be the presence of a round in the magazine or on the shell lifter. To be honest I'm as stumped as you. Just threw it out there as it seems like the only part that would wear out and cause any problems other than the bent shell stop you mentioned.

 

[Third_Rail]

I guess I wasn't as clear as I'd hoped!


The action jamming occurs with the magtube full or empty, or anywhere in between, but only after firing.

After clearing it, it acts like NOTHING is wrong and there wasn't ever a problem.

 

[Third_Rail]

Okay, anyone with a Mossberg 500a - how much should the shell stop be bent? If you can, a picture would be VERY helpful.

 

[mattw]

what is a shell stop?

 

[Third_Rail]

I figured it out, but here's your answer - the shell stop is a small strip of steel that has a hook on one end to hold the shells in the magazine tube.


It is number 39 in this schematic, and if you need I'll take a picture.

 

[DR]

What was the solution? I just took a couple of shots of my 500's shell stop but it sounds like you don't need them.

 

[Third_Rail]

Well, the shell stop was bent on the large portion, and straight on the thin portion - the exact opposite it should've been.

It was closer to an very gentle S curve than a wide V which it should be. I ran some dummies through it a few dozen times, and no more double feeds have occured.

I'm still puzzled about the action jamming after firing sometimes.

 

[Fred Fuller]

Don't try straightening that shell stop- replace it with a new one. It shouldn't cost more than a few $$ to get it, and that's not something to play around with. It's a critical part and it needs to be right, plus continuing to use it in an improper configuration could easily damage other parts of the gun's action permanently.

And see if you can get your original bolt assy back, and order a new firing pin and any related parts (retaining pin, spring etc.) when you order the shell stop. I dunno if bolts are interchangeable between gauges on Mossies or not, but if it was running OK with the original bolt I would put it back in if I could get hands on it.

Hope that fixes it,

lpl/nc (Hint: Time to go shotgun shopping.)

 

[Third_Rail]

Well, it truly works fine with the fixed shell stop - problem is I don't have the $10 or so to buy a new one. I've e-mailed the man I bought it from and we'll see where I can go from there.


As to replace, not fix - in most cases that would be the correct thing to do, but I trust my life with my abilities to fix things. In this case, I've got to due to money.

 

[mnrivrat]

OK , since the 20ga. & 12ga. bolts are not interchangable I am confused ?

Is your gun a 12ga. ? And if so, are you sure he put a whole 20ga. bolt assy in it ? Cause that don't pass the smell test for me.

As far as straightening the shell stop/latch , I have done many over the years and it typically turns out just fine. And I have never had one come back in over a decade of tweaking them. I've probably tweaked as many new factory stops as I have older worn ones.

It also isn't a real expensive item and can be changed whenever the cash is available.

There are all kinds of ways to creat a jam and also different types of jams so that is hard to anaylis without very specific details. One thing to look for is a dirty/rusty chamber. This is a problem that creats jamming by having the empty drop off the bolt face before it gets to the ejector because the shell casing has too much drag from the rust/dirt in the chamber.

Often times jamming is caused by that shell stop/latch not working properly so you may have already fixed both problems.

 

[Third_Rail]

I looked at the problems a bit further - After dry firing the shotgun with a dummy round, I held the forend forward and slammed the butt into the floor HARD. This didn't do anything, so I may very well have solved both problems.


The chamber is clean, and the action is spotless. I'm a little obsessive about cleaning things.


As to the nature of the problem with the jam - it wasn't slipping off the bolt, if anything it was REALLY on there. I had to take the barrel off whenever it did that, pop the shell off the boltface and then empty the mag tube. After that, I would work the action forward a bit then pull back hard until it came free.



As to the bolt - he SAID it was 20ga, but then I may be remembering incorrectly. All I know is that it isn't the same bolt, because mine had jeweling and this one doesn't. If he still has it, I'll get it back from him. If not, oh well.

 

[scout26]

Third Rail,

Send me an e-mail with your addy, I've got a shell stop and interupter for a 500 here in my box of Mossy parts. Free to a good home.

As far as jamming. I hate to ask the stupid question, but what length shells are you shooting ???

 

[mnrivrat]

As to the nature of the problem with the jam - it wasn't slipping off the bolt, if anything it was REALLY on there.

If it's a 20ga. bolt I can see why it would realy be on there, because the bolt face is smaller and the extractors would realy hang onto a 12ga. shell. I realy think you need to check that out before shooting again. Make real sure you have the correct bolt in the gun.

 

[Third_Rail]

scout26, thanks for the offer, I sent an e-mail.

Shells are 2 3/4", in a 2 3/4" chamber. Says so right on the barrel.


The bolt very well may be a 20ga, as it has an awful lot of play to it inside the receiver.

 

[scout26]

Parts will be in the mail tomorrow.

 

[Third_Rail]

I'll most likely end up replacing both and keeping them for "just in case". You sure are quite nice to do this, as it'll contribute to my feeling of safety - no more guessing if it'll work if I need it.

 

[Third_Rail]

Update - the shell stop fit and works like a charm (as does the original that I re-bent), but the interrupter isn't the same shape, so it won't work. The last shell has trouble coming out, so I'm going to order another spring and see if I can fix that problem as well.


With the shell stop bent wrong (as it was originally), I noticed that the action would jam with the dummy rounds occasionally; I finally got it to and figured out what made it do that - the interruptor would dig in to the shell a bit and jam the action until all tension (barrel, etc) was released from the bolt and it could move a tiny bit. D'oh!


I'll keep you all updated.