Mossberg 590 safety does not work - gun fires with safety ON

[lloydkristmas]

My brother had a problem with his Mossberg 500, so he sold it and got a model 590. Apparently he was installing an aftermarket stock of some sort and screwed the stock screw into the reciever too far. It must have damaged something inside the gun, because now the gun will fire/trigger will pull regardless of whether the safety is engaged.

Next course of action is to send it into Mossberg I guess. Just a warning to any others who might be planning similar modifications, the safety is vulnerable to damage when messing with the stock screw.

[CumbiaDude]

I think I've heard something similar before. Not sure exactly what the problem is, but the safety is pretty simple on the Mossberg. It's just a chunk of metal inside with a sliding part on the outside and a thin gasket and a ball bearing in between. The outer part could be broken (cracked) if it's a typical plastic part (which it probably is, if it's a 590 instead of a 590A1), or maybe the inner part is jacked up somehow. If it were *ME*, I'd just take the opportunity to take it apart and replace the safety myself (with an aluminum slider that won't crack), but if the inner metal part is broken you'd have to replace that. Maybe easier just to send it to Mossberg *shrug*

[DMR]

The saftey has a Safety Block on the inside of the receiver which interlocks with the connector in the trigger group. If you insert a stock bolt that is to long it will interfer with, or break the connector.

Remove the stock and then remove the trigger group. If the piece in the back is not sticking up you have broken the connector and will need to have it replaced. I'll see if I can get you a pic of the part.

the connector is what breacks, part 13 in the scematic from Brownell's:

Connector, SKU #:631-000-234

[nhskull21]

Common problem with mossbergs. We have 500's and 590's at work and one of the 500's has an aftermarket collaspeable stock and it doesnt matter where the safety is it will fire. Believe is a knoxx stock, our 590's with mesa tactical collapseable stocks havent had the problem yet.

[Robb Jensen]

My brother had a problem with his Mossberg 500, so he sold it and got a model 590. Apparently he was installing an aftermarket stock of some sort and screwed the stock screw into the reciever too far. It must have damaged something inside the gun, because now the gun will fire/trigger will pull regardless of whether the safety is engaged.

Next course of action is to send it into Mossberg I guess. Just a warning to any others who might be planning similar modifications, the safety is vulnerable to damage when messing with the stock screw.

You may have broken the safety installing the stock. I'd recommend taking this to a Mossberg Armorer, a qualified gunsmith or the best choice is sending it back to Mossberg.

[m24shooter]

OP:
What you're describing is a bent or broken connector, as DMR describes. It is a common issue with people that change stocks or stock bolts. The new stock bolt is too long, or the proper washer/spacer isn't used and the bolt ends up protruding into the receiver too far and it bends or breaks that connector.
When the safety slider is in the rearmost position, that connector rests against the internal safety block and the trigger will not release. When the slider is forward, the connector doesn't engage the block and the trigger can release. When the connector is bent or broken, there is nothing stopping the trigger at any time.
You're going to need a new connector.

I think I've heard something similar before. Not sure exactly what the problem is, but the safety is pretty simple on the Mossberg. It's just a chunk of metal inside with a sliding part on the outside and a thin gasket and a ball bearing in between. The outer part could be broken (cracked) if it's a typical plastic part (which it probably is, if it's a 590 instead of a 590A1), or maybe the inner part is jacked up somehow. If it were *ME*, I'd just take the opportunity to take it apart and replace the safety myself (with an aluminum slider that won't crack), but if the inner metal part is broken you'd have to replace that. Maybe easier just to send it to Mossberg *shrug*

What you're describing is a different issue. The plastic safety sliders (particularly with the old models) were prone to wear on the bottom. The detent recess would wear and the safety would either re-engage after every shot or the safety would just quit working. The metal wear plate on the bottom of the newer safeties is also there to keep the recess from opening up more.
The newer material in the plastic safeties is supposed to be much better. The aluminum A1 model pretty much eliminates the problem. There are also several other aluminum aftermarket models and one or two steel models.
As a matter of best practice, I replace any plastic 590 safety with a metal one just for insurance.

Common problem with mossbergs. We have 500's and 590's at work and one of the 500's has an aftermarket collaspeable stock and it doesnt matter where the safety is it will fire. Believe is a knoxx stock, our 590's with mesa tactical collapseable stocks havent had the problem yet.

Not exactly. It is a problem with some users that replace the stock or stock bolt and use a bolt that is too long or doesn't have the right spacers or washers.
If the safety isn't functioning then it needs to be determined if it is a wear issue or a connector issue, or possibly some other cause. If it is the connector and the Mesa stock guns aren't showing it then they won't show it because they were probably installed correctly or at least with the right hardware. If it is a wear issue, they may show it with more use.
If that is a duty gun and the safety is inop WTF is the armorer doing about it? That is asking for problems. Even if you don't have an armorer that is a situation that requires fixing. All it takes is one OIS with that gun that doesn't go just right and your department will have all kinds of problems.
Give a shout to Mike Shain at Aimpro Tactical in Colorado. He is the Mossberg LE service guy. He should be able to get that gun squared away.
http://www.aimprotactical.com/
Info@AIMPROtactical.com
303-838-7410
800-399-1354

ETA: Somebody sent me an email link with a Youtube video of some doofus "fixing" his connector that he bent doing the exact same thing you describe. He hammered it back into shape and it started working again. His video showed the part and his fix. You might be able to find it if you search for it.
Personally and professionally there is no way I would use that fix. I would either order a replacement that didn't get bent out of shape and then beaten back or I would take it to a competent gunsmith if you don't have the skill and tools.

[Robb Jensen]

Mossberg doesn't sell any components in the trigger group. If you broken or damaged something there they you have to replace the entire trigger group (liability). Brownells sells them but unless you have experience pulling apart the trigger group then I wouldn't recommend trying.

[CumbiaDude]

The metal wear plate on the bottom of the newer safeties is also there to keep the recess from opening up more.

Oh really? I didn't know this. I just heard people having trouble with the plastic cracking and decided to replace mine with a metal one (just a regular one, didn't get one of those fancy ones with the extra "wing" for the thumb).

Thx for the info

[m24shooter]

The plastic ones can crack, and have cracked. Those are obvious when they happen and in some cases will still allow the safety to function normally, sort of.
The wallowing out and wear of the detent recess on the bottom of the safety slider is less obvious without removal of the safety (which typically isn't done due to the safety screw) and usually shows as the shotgun going back on safe after every firing or some other problem.