Mossy 500A with a safety problem

Overboost44 · Jan 18, 2019

I have watched all the video's I can find but I see nothing about this issue.

Took the gun apart to clean it and replace the foregrip, barrel and eventually the stock. Put it back together and when you put the trigger pack back in you leave the gun in the safe mode. I do that, try to fire it and the safety works fine. I rack it, take the safety off and it fires. I then rack the action, put the safety on and if i pull hard enough, it fires. Something is obviously wrong. I have done this a dozen times I get the same results.

Attached are some pictures. Does something look worn? Should I consider replacing the safety block (the part on the inside of the receiver) or should I replace the trigger pack (more expensive). Am I missing something?

John from MD · Jan 18, 2019

How old is that 500 of yours?

gwchem · Jan 18, 2019

Pull the safety selector and compare to the picture on numrich or some other parts website. I have a similar model and the end of the safety switch broke off. Does yours look like it's hitting the L shaped part in your second picture?

John from MD · Jan 18, 2019

The safeties, while in the same location, are different on earlier models. The safety detent holes could be worn but I don' t recall if the later safety detent plate can be installed on an older gun.

Op, did you take the saftey apart when you were changing the stock?

Doco Overboard · Jan 18, 2019

It's been awhile but faintly I remember the problem being accumulated dirt/grime in the trigger housing. Had the same or similar problem on a BPS now that I'm starting to think about it. I seem to recall it was only a little bit that made it act up.
I over looked it a few times intentionally before I finally convinced my self to clear it out.
Second guessing now, but it could have been behind the safety tab itself. At any rate, nothing needed completely disassembled to remedy the problem. Dental pick did the trick.
Same problem as you described.

Biggfoot44 · Jan 18, 2019

Did the gun do this before you took it apart ?

Doco Overboard · Jan 18, 2019

The action lock lever is real long on the 500, Im starting to convince my self it was something under it, or the tuning fork looking trigger connector. Look right where it stops at the bottom of the housing. With the pack out of the receiver, the crud didn't allow it to travel low enough, made the safety stiff.

Overboost44 · Jan 18, 2019

John from MD said:
How old is that 500 of yours?

It is old but I don't know the age. Does Mossberg have a serial number reference? I got this at an estate auction at HoCo Fairgrounds about 2yrs ago for $120. Single slide bar and metal safety.

gwchem said:
Pull the safety selector and compare to the picture on numrich or some other parts website. I have a similar model and the end of the safety switch broke off. Does yours look like it's hitting the L shaped part in your second picture?

It looks to me like the angle on the trigger that catches the safety block would be a very slick surface to sit on the safety block but it looks just like the one on Numrich. It does look like they touch as I see the wear mark on the safety in that second picture.

John from MD said:
The safeties, while in the same location, are different on earlier models. The safety detent holes could be worn but I don' t recall if the later safety detent plate can be installed on an older gun.

Op, did you take the saftey apart when you were changing the stock?

I took the safety apart when I couldn't get it working correctly. I thought there may be room for sliding the catch slightly forward or back but it does not.

Biggfoot44 said:
Did the gun do this before you took it apart ?

That is the million dollar question. I can't be 100% on that. I am fairly certain it worked properly.

Doco Overboard said:
The action lock lever is real long on the 500, Im starting to convince my self it was something under it, or the tuning fork looking trigger connector. Look right where it stops at the bottom of the housing. With the pack out of the receiver, the crud didn't allow it to travel low enough, made the safety stiff.

I will do that next and clean out the trigger. That said it seems the safety button runs out of room on safe before it full catches where it is supposed to hit the trigger. Like it is bent.

I really appreciate all of you guys trying to help me figure out the mystery. I do have a 20ga 500 here. Maybe the trigger packs are interchangeable just for testing?

Overboost44 · Jan 18, 2019

Answered my own question on the interchangeable trigger packs. The 20 ga will not work in the 12 ga.

Overboost44 · Jan 18, 2019

John from MD said:
How old is that 500 of yours?

Looks like 1970 from the serial number list that I found on the Mossberg owners website.

Mossy 500A with a safety problem

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