Why does the forearm on my Mossberg 590 pump shotgun lock up sometimes and prevent hull from ejecting?

DougC

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During a match after 50-60 rounds I am not able to eject the spent round as the forearm will not retract. After much effort I can get the round ejected and then the gun runs OK. Any suggestions?
 

zackmars

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Are you by chance twisting the pump when trying to pull back?

Is the chamber clean? Have you tried different types of ammo?
 

Big Dipper

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I have had the same issue when using cheap, steel base ammo in both a Mossberg 500 and a Remington 870.

The expansion of the steel base combined with the ”canting” of the shell by the hook type extractor makes it impossible for the extractor to pull the shell out, with almost no clearance. The extractors in an O/U pull on nearly 1/3 of the rim so there is never a problem.

The extra heat from the 50 - 60 rounds may also be reducing the clearance by causing the chamber to shrink a tad.

The next time it happens try dropping a cleaning rod down the barrel while you are shucking the shotgun. That helps to get the shell going straight back without the cant.

Also consider using a higher quality shell.
 

DougC

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During a match after 50-60 rounds I am not able to eject the spent round as the forearm will not retract. After much effort I can get the round ejected and then the gun runs OK. Any suggestions?
Thanks all for the suggestions. I am using Winchester Super Target and Federal Field and Tgt loads; #8 shot. During match there is usually 30-40 minutes between shooting so the gun cools off. Its possible the gun lube is wearing off during match so I will try adding lube in-between stages. It is not practical to drop a cleaning rod down barrel as I am actively engaged in the stage match and that would be a lot of time and safety issue on the range. I just have to muscle the forearm to rear to get the shell to eject and suffer extra time.

BTW: I am reaching out to this forum after this reply from Mossberg Customer service. I quote

"Thank you for your email. Based on your serial number the shotgun you have is 22 years old. Unfortunately, this is a very odd thing due to the fact it does it briefly and then works fine again. Especially with it being cleaned regularly."
 

tonelar

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Can you give it a quick clean and lube mid match?

When I go over 30-40 shells in a match, I usually go to my second shotgun.
 
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Glenn B

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In my experience, seeing this happen to scores of shooters at the range over many years, it is almost always due to shooter error in as much as the shooter is not using enough force to pull back the slide or is short stroking it. It is as simple as that in most cases; although, it can be due to ammo or a malfunction of the gun. The thing is you said this:
After much effort I can get the round ejected and then the gun runs OK. Any suggestions?
That almost always indicates user error (weakness in operating the slide or short stroking the slide). I base that finding on my experience as a LE firearms instructor for about 16 years and having witnessed it happen time & time again usually with the same shooters over the years; although, it occasionally can happen to anyone. I would check the gun by taking it and operating it myself and if I could do it without a problem - then give it back to the shooter who then operated it without a problem after instruction not to short stroke and to use enough force to operate the slide - I chalked it up to user error. It can happen to anyone including myself even though the shotgun was one of my favorite weapons with which I practiced profusely and the damage to my right shoulder can attest to how much I used the 870.

By the way, most shooters who have this problem rarely want to admit it is user error at first. Most will try to say the gun is dirty, not lubed enough (as if 40 or 50 rounds should foul it so much it will not operate correctly) or that the ammo is faulty. The truth is firing a 12 gauge, even with field loads, stresses your muscles and skeletal structure to the point where you may either use less force or short stroke. When you put your mind and muscle to it though, it suddenly works again and that in and of itself reveals wherein the problem likely is to be found. When you are firng slugs or 00 buck, it tends to happen more frequently for some shooters.
 
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DFW_Warrior

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Can you give it a quick clean and lube mid match?

When I go over 30-40 shells in a match, I usually go to my second shotgun.
Wait what!?!?! Of my two competition shotguns for 3-gun (Benelli M2 for Tac Ops and a Stoeger P3000 pump for Heavy), neither one of them really needs any attention for many many hundreds of rounds or more. No joke or embellishment at all here but my M2 has close to 25k rounds on it and has only been cleaned at most maybe 6-8 times ever. My P3000 is much newer and has only seen a few seasons of competition so the round count is much lower but I actually haven't taken it apart and cleaned it since putting it into service. It has been used in 2 or 3 dozen competitions since then, many of them being 150-200 rounds each. If you can't get more than 30-40 rounds out of a gun then there are some other problems going on there.

For the OP, with what it posted it could be any number of things from poor technique to ammo/gun compatibility, to maybe a gun problem, or even just chalk it up to "sometimes those things just happen". Like @Glenn B said, short stroking is a real thing and despite having a whole bunch of rounds through my P3000, in the heat of a stage I can 100% forget to rack that thing the way it needs to be racked and it will lock up on me. It happens even to the best shooters at a match at certain times.
 

Pachucko

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OP,

Maybe polish the chamber a little if you never have? There's a thousand tutorial articles and YouTube vids on how to do it.
 
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Axxe55

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Pump shotguns are made to be racked with vigor and authority, not delicately.
 
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