Desperately need Beretta shotgun mechanic

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  • amboy49

    Master
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    Feb 1, 2013
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    central indiana
    I have a Beretta Tekneys 391 20 ga semi auto shotgun. The gun has had limited use. I purchased this gun from someone on another forum. The gun will not eject fired hulls nor feed the next hull from the magazine. I have cleaned it till it looks like it just came from the factory down to dismantling the magazine tube and removing the stock and cleaning the recoil spring assembly.

    New shells or reloads make no difference ! Same problem ! Hoping to find someone around the Indy area or extended suburb.
     

    Twangbanger

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    Can you poke a small allen wrench through the 2 gas portholes in the barrel?

    Are you sure it's not missing the snap-ring thingey on the gas piston? I'm going from memory here, but I had a 390 do this, and this was the problem. I don't know why the previous owner would have removed it, but it was gone. It was not something I would have noticed without having the exact correct part for comparison.

    I don't have a 391, but still have two 390s, and will break one down to see if I have any epiphanies...
     

    amboy49

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    I’ve cleaned the barrel gas ports with a small twist drill after removing/cleaning the gas valve components. Removed the trigger group and cleaned the magazine tube parts and the recoil spring in the stock ! Relplaced the magazine spring. Have ordered a new recoil spring.
     

    Twangbanger

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    Next I would check your piston. If you look at the rearward or "closed" end of the piston, it should have 4 ears that push against the action sleeve, and in the center of there, should be a bushing assembly in the center hole. It's held in place by a snap ring, and it chokes down the ID of the clearance hole where the threaded rod goes through. If those bushing components are not all present, that hole will be too large, and you are getting gas blow-by of the piston, losing all the gas power to operate the action. You would be able to pull the spent shell back out of the chamber easily by manually operating the bolt handle (ie, the shell is not stuck in the chamber or anything like that), but the gun is simply unable to operate itself due to this internal gas leakage going to a place where it can't drive the gun. I was running three 390 competition guns when I shot trap, and one of them had this problem when I bought it used. The gun would fire and the bolt might back up just the slightest little bit, then pop back shut. Swapped out pistons and it went away.

    I really hope that's it. I don't have a 391 in front of me, but the 390 system is very similar. (If that's not it, then we get into weird things, like did somebody put a really super light aftermarket gas regulating spring in the gun and it's letting all the gas out the forward forearm vent, etc.).
     

    amboy49

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    I’m 99% certain all of the piston parts are there. A replacement recoil spring came with the gun and I’ve installed that. The gun also came with two springs for the gas valve. I’ve tried using both with no correction to the issue. I’ve ordered a new magazine spring and will try that. The gun also came with two pistons, an original Beretta and one from Coles. Swapped them with no change.
     

    Twangbanger

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    When you say "fails to eject," does the bolt just sit stationary upon firing, or does it come back then slam the empty stuck in the port?

    Running short on ideas but since it's a 20 gauge, I'm wondering if someone messed with the mag cutoff and removed/stubbed the ejector to turn it into a soft recoiling single-shot for a kid to use? It really makes no sense, but I've seen people do dumber things with guns.
     

    amboy49

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    Feb 1, 2013
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    central indiana
    When you say "fails to eject," does the bolt just sit stationary upon firing, or does it come back then slam the empty stuck in the port?

    Running short on ideas but since it's a 20 gauge, I'm wondering if someone messed with the mag cutoff and removed/stubbed the ejector to turn it into a soft recoiling single-shot for a kid to use? It really makes no sense, but I've seen people do dumber things with guns.

    ”Fails to eject” meaning the bolt will come back about three quarters of the way and stop without the shell being ejected. Occasionally the bolt will move to the rear but then move forward with the fired hull remaining in the chamber. The ejector is working properly so that’s not the problem. I have put in a new magazine spring and a new recoil spring. I am shooting 7/8 oz loads moving 1,200 fps - both factory and reloads. I haven’t tried any “hot” shells yet. - say 1,300 FPS.

    I’ve stripped and cleaned the entire gun including the gas valve, piston, etc. Lubricated (with oil) all areas should should require it. Someone suggested it could be a bent magazine carrier, but another said that’s not an issue with the 20 ga. I found a recoil reducer in the stock which I think I will remove and see what happens. I called the seller and explained the problem and, of course, he said he never experienced any problem like what I’m describing ! Hate to spend additional dollars over and above the purchase price but I am very near to sending it to Beretta or Cole’s Gunsmithing. That will add at least $30 bucks each way for shipping/insurance plus labor and any parts. I’m thinking it’s bound to add, at minimum, $110-$200 to the cost of the gun.
     

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    Twangbanger

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    Ah crap! A "TS.com" gun full of aftermarket parts. At minimum, with two springs and two pistons, you know somebody's been messing with the gas system components, trying to accomplish heaven knows what. The nightmare scenario is somebody started reaming out the gas ports in the barrel trying to get superlight loads to function, went too far and had to compensate with other downstream components, couldn't figure it out and gave up.


    I would email Joe B. at Tronspace, or Cole's, and ask what you should be looking for. The only significant part of the gas system you haven't changed out is the barrel, and that's the most expensive.

    Good luck with your purchase. I hate it when people do stuff like that. There is a video out there of a lady USPSA competitor who spent a year+ rehabbing her leg from a gunshot wound, because she bought a used pistol from someone who had messed with the trigger and it went off in the holster without her touching it, as attested by the RO who was running the timer when she went down. Your example isn't as evil, but still really frustrating.
     
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