Stock collapsing when firing, chargin handle concerns/questions

Discussion in 'RDB Bullpup Rifle' started by pbnationrc, Aug 9, 2020.

  1. pbnationrc

    pbnationrc Member

    88
    Dec 19, 2009
    I am pretty sure I have the gas adjusted correctly. Brass looks great, cycles great. Just the stock collapses after a couple of rounds.

    Secondly, hen I fire the charging handle comes out of its resting place up front and rests about an inch back and doesn't move back home. Whats up? I do notice when the gas is not adjusted correctly it will rest halfway back.

    Third, when I exhaust a mag the charging handle comes back and stops about 1 inch too short to lock fully back and up into the cool MP5 spot. The bolt does lock back so I can change mags but I can't do the MP5 slap to look cool. Because it is about an inch forward and not locked up. The only way to release the bolt is the little button above the mag.

    Thanks
     
  2. iamscottasus

    iamscottasus Well-Known Member

    Feb 21, 2014
    This has been reported by others. The handle is non-reciprocating so if its not locked forward, it will flop around.
    It appears there may be a problem with the spring tension on the handle catch not keeping it hooked on the gas block.
    I can see that handle winging loose under recoil.
    I have yet to try mine.
     

  3. anach

    anach Member

    12
    Jul 18, 2020
    This is in a defender/survival? I'm taking mine to the range this week, but I haven't been able to get the stock latch to fail messing with it at home. Is the stock latch resting on the rounded weld bead of the receiver or the vertical wall? If the weld is a little bit too deep, I could totally see it camming over the bead under recoil.
    IMG_20200809_221948062_HDR-1.jpg
    If you're feeling brave, you could try to remove some material where the tabs of the latch sit in the stock. That would let the latch sit further from the weld bead and maybe not slip under recoil. That or contact Kel-tec and yell at them since a stock that doesn't actually work extended may or may not meet BATF requirements...;) it is the serialized component though, so expect it to be a total pain in the rear.

    Like iamscottasus noted, the hook on the front of the charging handle might not have enough spring pressure to grab the wings on the gas block. Mine is pretty weak. If it's a defender, they're new enough that the fixed handle might have the center of mass too far from the pivot and it's popping off during recoil. A stronger spring might be the solution.
    The hanging up halfway when undergassed is a little weird. There should still be spring pressure behind the handle to get it mostly forward, if not all the way into lock.

    This is a consequence of the non-reciprocating charging handle as well as mechanical realities. It'd be mechanically difficult to have a last round hold open actuated by the magazine rotate a charging handle into the lock position, even on a reciprocating charging handle.
    Note, the mp5 doesn't lock the handle back on empty either, and the manual of arms for the mp5 is to drop the empty mag, pull the charging handle to the rear and lock in the notch, then insert a new mag, then slap it home. Not sure about the G3 or FAL, but I assume they're similar.

    The easiest way to drop the bolt after going dry would probably be to pull the charging handle back just a tad, then let it go. You just need to release the pressure on the bolt catch a tiny bit and it'll drop out of the way. Lucky irishman sells a doodad that gives you some mechanical advantage on the bolt release button if you want to use it as you insert a new mag.
     
  4. anach

    anach Member

    12
    Jul 18, 2020
    Not to derail too much, but the stock on a non-S/D model can't physically collapse, so I'm not sure why you are bringing them into this. The stock on the S/D models attach to the receiver and can be extended and locked in place with a latch that rests on the rear of the receiver. If the weld bead is the problem like I hypothesized, then a new stock isn't going to help. They'll need to fix the receiver, which will require FFL shipping, hence the pain in the rear. It should be an easy fix if they have brains at all.
     
  5. iamscottasus

    iamscottasus Well-Known Member

    Feb 21, 2014
    Im just guessing but I think the last round bolt hold open bolt position may be further back than the rear charge handle notch?
    You should be able to charge from the notch, but its not going to stop in the notch on a last round, yea, there goes the cool factor.
    But, hey, you could try slapping the top of the receiver! Maybe the catch arms will release if hit hard enuf!
    You could remove the bolt hold arms altogether so you have to use the handle.
    (Iv'e actually considered this).
    But since the bolt is cast from melted down Hot Wheels, I doubt it would take much of a pounding.
     
    Last edited: Aug 10, 2020
  6. WolfWings

    WolfWings Well-Known Member

    298
    Feb 19, 2020
    Kansas City
    Ah, sorry, the sentence phrasing sounded like you were saying KT should replace the stock. Mea culpa! Deleting my post to avoid cluttering the thread. :)
     
  7. pbnationrc

    pbnationrc Member

    88
    Dec 19, 2009
    To answer anach, I have a Defender. The latch is resting on the straight wall part but just a c*** hair (official measurement) or two above the rounded part.

    Well, at least I know my old toys were put to good use and not in a land fill somewhere!
     
    iamscottasus likes this.
  8. anach

    anach Member

    12
    Jul 18, 2020
    @pbnationrc, Cool, I'll see if mine does the same thing in live fire. You could try filing under the tab to get the latch onto more of the straight part (just a few more hairs). That would be the easiest fix and really hard to bugger up, even if you aren't super handy. If it doesn't fix it, I'd say Kel-Tec really screwed something up with the back of the receiver or the latch bend angle on yours.

    @WolfWings, no worries. I could have been clearer.
     
    WolfWings likes this.
  9. anach

    anach Member

    12
    Jul 18, 2020
    Went to the range today, first shot, the stock collapsed. Kel-Tec must've gotten the bend angle of the latch wrong or something.
     
  10. pbnationrc

    pbnationrc Member

    88
    Dec 19, 2009
    I went to the range again a couple times and its not doing it. I really messed with the gas system, took my silencer on and off and again adjusted the gas and it seems to be shooting good now. I will keep watching it though.
     
    iamscottasus likes this.