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Mossberg 590 Pump Action Troubleshooting


Staff member
Any issues, concerns or problems you may have with your mossberg 590 pump action; this is a thread for troubleshooting.
Oh man... I get to be the first to post a problem! Okay, so hitting the slide release my gun is still as smooth as ever. But after firing a round, or dry firing it's pretty stiff. I've broken it down a few times, checked parts. everything is clean and undamaged. It's not the bolt having trouble disengaging either. The trouble is after that point. Any ideas?
Guess I never closed this out. Somehow the bolt lock lug got really dirty and was sticking a bit in the bolt. Saturated it with Hoppe's, lightly lubed, and the problem went away. I was running lots of different cheap, on sale buck and slugs, but I'm not sure how it got so dirty there.
Not a problem, but a question.

I was running through the gun after getting it home and there is a plug inside the mag tube behind the cap and I don't want to force anything, and it seems pretty snug in there. How do you get that out to clean inside there?

hi bros.. newbie question. i tried striping my 590 awhile go. all went ok but unfortunately the mag tube was stuck. how do i remove it? any special tools? im tempted to use my vice but was torn that i might break it. thanks in advance
Wow, this is very encouraging. When I first looked at this thread I thought there would be all sorts of posts about problems with the 590, but seeing that there is only one, I feel good about having bought one.
VTX said:
Wow, this is very encouraging. When I first looked at this thread I thought there would be all sorts of posts about problems with the 590, but seeing that there is only one, I feel good about having bought one.

Nope, no real issues. Youre good to go!
Mossberg 590 Auto Safety Problem Fix with Pics

Mossberg Auto Safety Problem. Long Post but informative as to how to fix.

I had a very annoying problem with my Mossberg 590 12 gauge. The safety would become slightly engaged after working the action. Pump shotgun with an auto safety. Great. The condition wouldn’t happen every time either. I did some research on the internet. There were a lot of posts about the disappearing safety and problems related to that occurrence. A lot of people posted that it could be recoil causing your hand or thumb to engage the safety while recoiling. I thought this was happening. So I tried shooting with my thumb unwrapped. It would still happen. I came to the conclusion that the spring loaded ball that keeps the safety in position was either missing or weak. So off to Brownells I went. I ordered a nice oversized steel safety with a raised up stud sold under their name. That piece is nice and makes the safety fool proof to manipulate. I replaced the spring and ball bearing with new ones. When you use a steel safety on the Mossberg the thin oblong washer is not necessary. This piece started with the plastic button. It doesn’t hurt anything to use it though.

I installed the safety screw with blue loctite. The safety felt good but I wanted it more positive. So I lightly deepened the holes so the safety has a more positive snap on and off. Nice stiff feeling. Took it and ran the shotgun very rapidly to try and replicate the problem. I started having auto safety issues again. I was disheartened that my fix had not worked. I watched the AGI Gunsmith DVD on the Mossberg 500 Series shotguns. For those who don’t know the Mossberg 500 is almost identical in parts and function to the 590, 590a1, Maverick 88, a Sears Model, and a couple others I don’t remember. The DVD goes over all these shotguns but basically they all function the same and have either heavier duty pieces ( 590a1 Barrel and Aluminum trigger Guard ) or less expensive ( Maverick 88 ). The DVD went into nice detail about function, disassembly, reassembly, and even had trouble shooting. There was nothing mentioned about the Auto Safety Problem I was having.

I left the shotgun alone for a while until I went to a Zombie Shooting match. I knew about the safety issue so I wanted to fix it. I took the gun apart and cleaned the heck out of the trigger guard, receiver, and especially the safety area. There was a lot of gunk. So I hoped that would fix it. I examined how the parts move inside the receiver. I reassembled and worked the slide forcefully. When the slide was worked hard something was hitting the safety and moving it an eight of an inch on safe. I shot about 30 rounds at the match and then it started switching on occasionally. I tried to run the pump surely but not to hard to minimize the auto safety. This worked 90 percent. I was disappointed still.

This is an ex police 590 9 shot with factory heatshield and an M16 bayonet lug. These things are supposed to be tough. I tricked it out with a Tritium XS Sights banded front sight and a Factory Mossberg rear Ghostring ring. It looks like its ready for anything but not with an auto safety. I still wanted to fix the gun. I didn’t want to sell it and let someone else deal with the problem or maybe not even know about the problem. I searched more and found a few people were posting the same symptoms. There were a few suggestions as what to look for. But there were so many postings by people that wanted to help but clearly had no clue what the problem was. Approach anything you read on a web forum as gunsmith advice with absolute doubt. The one good bit I read was that the replacement screw for the safety might be to long and letting part of the bolt hit the safety. I took the shotgun back apart and checked this but the screw was hidden inside the safety. I did see a line that was a wear mark at the front of the safety. This is where the safety was getting knocked on. I had read that the back of the firing pin could be striking the safety. This sounds possible and looks possible. There was some discussion about the frame being worn out and letting the bolt hit the safety. I closely examined the recesses inside the frame for wear or battering. There were no rail stops that had been worn away by the action being worked really hard.

The shotgun locks up into the steel barrel through a lug in the bolt that cams into a square hole in the barrel extension. So the frame does not get stretched by recoil. The steel barrel takes the recoil. So this is not a case of the gun being shot out or beat to death from recoil. Although there is so much crap about the aluminum receiver not being as tough as the steel on an Remington 870. I have both and the 870 and 590 are quality shotguns.

So I ordered another internal safety in case my repair didn’t work I would still have the factory parts. I examined the safety and here is a discussion of how it works. On the trigger group there is a small stud that sticks straight up. On the frame there L shaped piece of metal. The long portion of the L has a c crook in it. The short portion rides in a slot in the frame. That L piece is held up in the frame by a screw through the button on the outside. There are two holes in the bottom of the button. A ball bearing is pushed up into one of the two holes by a spring and keeps the safety in the selected position. When the safety is on the L shaped piece of metal sits over the stud in the trigger group and prevents the trigger from being pulled. When the safety is off the stud is unhindered and the trigger can pull to let the hammer go.

If you are at all unsure about doing this work. STOP and do not perform this work. This is not for amateurs. This is an advanced task. Take it to a gunsmith. Send it to the factory.
I examined the wear marks and determined that I could remove some metal from this point and not affected the safety operation or strength of this piece. On the short end of the L that rides in the frame, I put a slight bevel on the front edge of the safety. Please understand that this is not the piece that stops the stud from moving. This is the piece closest to the back of the bolt. I used a tiny pair of vise grips and a 1” belt sander to remove a small amount of metal from the front edge. I put the parts back together and racked the crap out of the slide and the safety would not move no matter how many times I worked the action. I took it out and test fired the shotgun with slugs, military buckshot, and Birdshot. Problem solved. After not finding answers on the internet I decided to take the time and post my problem and the fix I found to help out the next guy.


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Re: Mossberg 590 Auto Safety Problem Fix with Pics

I usually do not read any post longer than one screen long because most internet postings start to ramble on about things. But you made a nice write up for the majority of it. The pics at the end are super because I got lost only at the last two paragraphs and will need to re read them a few times because you did make great details on the parts and locations.

So the cliff notes version is you ground the leading edge of the safety to clear the top side rear end of the bolt that slides underneath. Awesome explaination of a problem, cause, and solution. Excellent work for your first rep point. Thx :ugeek:
Re: Mossberg 590 Auto Safety Problem Fix with Pics

Thank you for taking the time out and posting up this solution!
Re: Mossberg 590 Auto Safety Problem Fix with Pics

Great posting! Thanks for putting in the time to post all this, I'm certain it will be helpful!!!
Re: Mossberg 590 Auto Safety Problem Fix with Pics

I was having a safety problem and my fix was putting a little stretch in the spring that holds the detention ball. I developed the problem after putting on the recoil reducing stock. I think it was from the inertia of the barrel and receiver moving forward after firing heavier loads. Anyway it fixed the problem.

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Re: Mossberg 590 Auto Safety Problem Fix with Pics

Thanks for the encouragement.

Nasa. I originally thought mine was recoil related. You can check for this by racking your slide fast and hard with the safety on several times. The safety will move back slightly if it is making contact. My next upgrade was for a pistol grip grip stock and the Blackhawk recoil reducing AR style stock was one I was thinking about. My 590 is pretty heavy so the recoil is not as bad as a standard shotgun with buckshot. Would you describe the change in feel from your stock. Do you notice the shotgun return forward and stop from the springs in the stock. Is the spring stock great or just ok?
Re: Mossberg 590 Auto Safety Problem Fix with Pics

I was thinking of changing the name of mine from Blackhawk to Marshmallow, The Knoxx Blackhawk Spec-Ops recoil reducing stock mad the difference of night and day. Not a blood blister or bruises from my heaviest loads. On top of that, now I added the LimbSaver butt pad and 9 shots of #00 magnum in under 10 seconds with no pain. Make sure you wear ear plugs. I put a +5 extension on my 835.

Putting stretch into the detent spring just applied more pressure to the detent hold, keeping the inertia from setting the safety to the safe position.