Bad slide lock on Mossberg 500 - THR

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Old July 28, 2014, 11:57 PM   #1
4v50 Gary
Join Date: December 19, 2002
Posts: 16,424
Bad slide lock on Mossberg 500

Along with the action lock, the bolt slide keeps the bolt from unlocking. When the hammer is forward, it pushes the action lock down, allowing the bolt slide to be pushed rearward when the forearm is pushed to the rear.

I'm looking at the bolt slide that is rounded in the area where it contacts the action lock. Because of that, it doesn't take much pressure to push the forearm back without even having to depress the action lock. I know the bolt lock does rise to engage the slot in the barrel. When the barrel is removed and the action worked, I can see the bolt lock rise and fall.

Has anyone else out there ever found a defective Mossberg that can be released without depressing the action release?
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Old July 29, 2014, 12:55 PM   #2
Join Date: June 18, 2014
Posts: 6
Traded one off Sunday. It worked when I got rid of it, but I had to replace the bolt lock when I bought it. Which was no big deal as I bought it for the muzzleloader conversion barrel that was on it.
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Old July 29, 2014, 05:20 PM   #3
Join Date: January 15, 2008
Posts: 314
I've seen two and both were more or less from the same reason. On the first, the owner always pulled for fore end back hard while shooting. That makes the action stick after firing, so his answer was to pull harder. Eventually it bent the action lock and the trigger assembly and gouged the bolt slide to the point that it would no longer lock reliably when he pulled back hard.

The second was somewhat similar. The owner also pulled back hard while firing and had the action stick. His answer was to file and polish the contact surfaces between the bolt slide and action lock bar. And then file and polish again, then file and polish again. Now the slightest bump will unlock it when the foreend is pulled hard.
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Old July 30, 2014, 02:53 AM   #4
Join Date: December 24, 2002
Location: MN
Posts: 4,146
The first thing to do is to clean the trigger group making sure that the bolt lock lever has full travel. Sometimes gunk will build up between the bottom of the lever and the slot just forward of the manual release button . This prevents the the forward tip from coming up to fully contact the slide.

If that doesn't help you can remove a small amount of metal off the bottom of the slide lock bar where it makes contact with the frame. (again just forward of the button in the housing channel.

Yoy can also lightly bend the toward section of the bar upward to get more engagement.

And of course you could also just replace the release bar.
Their swords, and every other terrible implement of the soldier, are the birthright of an American... The unlimited power of the sword is not in the hands of either the federal or state government, but, where I trust in God it will ever remain, in the hands of the people" (Tench Coxe, Pennsylvania Gazette, Feb. 20, 1788)
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Old August 12, 2014, 08:00 PM   #5
4v50 Gary
Join Date: December 19, 2002
Posts: 16,424
I returned the old slide lock, a letter of explanation and my armorer's certificate to Mossberg. Today I received a replacement slide lock and fitted it. The bolt locks now and won't go back until the action released is depressed. Success!
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