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Thread: 870P problem. Does this locking block look okay?

  1. #1
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    870P problem. Does this locking block look okay?

    The background on this is that this 870P belonged to my job and was a range gun. It would give guys problems with locking up and being near impossible to work the action after firing. It only did this occasionally and since we try our best to "train like we fight" and all, when it happened no thorough examination of the failure was usually done at that time, just the instructor doing whatever it took to get the empty shell out. For the most part, for better or worse, when something goes wrong with equipment the assumption is that its the shooter until it happens to a known good shooter and a lot of the time these things are happening on a range, in the dark with four other guys on the line trying to qualify.

    Long story short, eventually it happened to a known good shooter and they found a broken ejector (ejector rail, I believe, definitely not just the spring). The shotgun went back to Remington and the ejector was replaced but it seems like that was just a symptom of the real problem. In talking to one of the firearms instructors he told me that they were still having a problem with the gun locking up after it had been fired and that since it was about time to replace the range shotguns anyway he would be taking it out of service. When we take guns out of service they are sold to a distributor and when I heard what the distributor was paying, for all my shit talking about 870s not being that great based largely on seeing problems with this very gun, I couldn't help but make an offer of my own. So now I have it, and I'm working on making it the gun it should be. Why wouldn't I want to take on this headache, right?

    Range time around here is limited and expensive so I'm trying to address any obvious issues before I take it out since I know that there is a problem.

    Since the locking up problem only ever occurs after it's been fired and never with dummy rounds or unspent shells, I was thinking it might be the common rough chamber. In searching around this definitely seems to be more of an Express problem and this is a P. Also, I felt the chamber as much as I could with my fingers and it actually felt pretty smooth, even compared to my Wingmaster that is at least 40 years old. Further, the only thing this shotgun has ever been fed are Remington Managed Recoil Slugs and Buckshot and, briefly Federal Flight Control Buckshot. ("Train as you fight" and all) None of the poorly regarded cheap Winchester rounds. Never the less, since there was really nothing to lose I did the bore brush/steel wool polishing job on it and now it feels really smooth.

    While doing that and checking over other parts I discovered what seems like an odd condition on the locking block and now I'm wondering if this could be the culprit. It is kind of flattened on the back edge of the part that locks into the barrel extension. Since it's part of the locking mechanism, I also want to confirm that the gun is safe before I try to find out if my chamber polish worked. Does this look okay?





    So, 870 experts, could this be the issue?

  2. #2
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    What does the barrel hood look like?

  3. #3
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    I'm not trying to be a jerk, but based on your range staff not checking the ejector tip on the 870 as part of cleaning and maint, or a quick look when they unFUBARED the stoppages, all I got to say is who knows.

    I don't suppose it has ever had go/no go gauges run on it? If so did it pass? Any chance that barrels got swapped around during a mass cleaning session?

    Was this shotgun ever run with a different bolt?

    What does the corresponding female part look like on the barrel hood? Any rough spots in there?

    Assuming the surface of the locking block's face is smooth, with no jagged edges, that shouldn't be a problem.

    You had enough of the triggerplate in one picture that I was able to see your action bar lock spring in place. Is the washer in place on the trigger pin?

    With that black bolt that shotgun isn't that very old, so I doubt that the receiver has been cycled enough to have a bunch of slop in the action bar rails, but you never know.

    Without more description on the stoppages and how they were reduced it is just spitballing, throwing things out.

  4. #4
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    Fair criticisms. The 870s aren't treated all that great, but those would be all the original parts. We're a small agency and there are only two 870s assigned as range guns. In fairness the our newer instructor is a lot more open to the possibilities of problems with guns and trying to figure out what's going on with them, but they probably only clean the things once a year.

    Here are some more pictures, I'll grab some of the trigger assembly and the locking block face when I get a chance.







    Barrel Out



    Barrel In




  5. #5
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    That shotgun still has a lot of life left in it. I'd have been glad to jump on it.

  6. #6
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    No idea but my 870 express locks up with reloads sometimes. I figured it was bad reloads as it's never happened with good high brass, although I don't shoot high brass much either.

  7. #7
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    Thanks 26 Inf, I figured it probably did. I also figured that the problem should be fixable, unless something was just built out of spec, but since all the parts seem to fit together just fine, that doesn't seem very likely. Here's the next picture dump.

    Trigger assembly: The carrier pivot tube appears to be installed backward which I'll switch later. It doesn't appear like that would really effect function though.




    Bolt Face and Face of Locking Block




    Bolt and Slide



  8. #8
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    Just a quick update, because I hate when people don't update these things:
    I finally got it to the range yesterday and it ran great and very smooth. Not one single hiccup with a WIDE variety of ammo from Brenneke slugs to some very old and mildewy Federal paper shelled bird shot that I found, which actually got a little sticky in the wood stocked Wingmaster.

  9. #9
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    Polishing the chamber addressed the issue?
    Train 2 Win

  10. #10
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    Everything in the pics looks fine.
    That little flat on top of the locking lug is normal with use. When racking to the rear, the little plate under the bolt first moves back, unlocking the bolt and then dragging it rearward. When you rack it forward, the plate drags the bolt forward, but it's pushing on the locking block, which is causing it to push up against the inside of the receiver and drag on it as it goes forward. So, you will get that little flat, actually it matches the radius in the top of the receiver, and a drag mark along the inside of the top of the receiver.
    Sounds like polishing the chamber fixed the problem.
    Occasionally, the tolerances work out to when the gun is fired, and the bolt is seated back against the locking lug in the barrel recess, the spring loaded locking arm that keeps the forearm forward gets in a bind, and won't retract out of the way. The gun won't open, and the lever would have to be pushed in, as if opening the action without firing. It may be difficult to push it in.
    I have only seen this a couple times, on newer guns. Older ones were better fitted.

    Sent from my SGP612 using Tapatalk
    NRA Life, SASS#40701, Glock Advanced Armorer
    Gunsmith for Unique Armament Creations LLC, 07/SOT

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