Flubbing USP

Discussion in 'Gun Building, Modifications & Repairs' started by LoEM_1942, Oct 28, 2020.

  1. LoEM_1942

    LoEM_1942 New Member

    12
    4
    Lady Lake
    Heyoo. So I came into possession of an HK45 and have been working to fix it. After replacing four parts and putting some elbow grease in, I've managed to improve it greatly, but it's still having this odd chambering issue. Basically it decides not to chamber a BB intermittently. Here's a video showcasing the issue:


    When the gas gets very low in the mag, it's also venting it half the time instead of kicking the slide back to a locked position. The magazine is fitting firmly, follower spring is taunt and the follower slides freely. So I'm pretty sure the issue isn't in the mag. The slide fits without play and slides freely when moved by hand. The barrel is clean and clear. I'm not sure how to check the packing for seal, but it seems in good condition with no deformities, cracks or signs of wear.

    Here are some pictures of the sidearm:
    https://imgur.com/a/JnCC2nW
     
  2. aotsukisho

    aotsukisho Well-Known Member

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    299
    Sounds like light striking, does the problem occur less when the mag is cold? Hammer spring might be weaker than spec. I'm assuming the nozzle is not damaged, pulls out smoothly and returns properly when manually racking the slide

    I've also had experience with multiple KWA guns where the main seal in the blowback unit gets hard and does not seal properly as it ages. Try pulling the blowback unit and inspecting the condition of the main seal
     

  3. Guges Mk3

    Guges Mk3 Well-Known Member Supporting Member Lifetime Supporter

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    If you have it torn down to that part, also check the nozzle for a crack.
     
  4. LoEM_1942

    LoEM_1942 New Member

    12
    4
    Lady Lake
    Issue is constant regardless of mag temp.


    Just tore it down completely to inspect the nozzle. Doesn't look like it's cracked or damaged. The blowback seal does appear hardened. Wasn't sure initially if that was how it was supposed to be, but after comparing it to my G17, it's significantly harder (albeit undamaged). So it looks like I'm hunting for a new one.

    As for the nozzle, it does stick a bit more in the packing than my G17's does before pulling free. Yet it does seem to pull free consistently and smoothly once it does. I'll post a video clip later if necessary. Is that a potential issue and do I need to lubricate the packing?
     
  5. Guges Mk3

    Guges Mk3 Well-Known Member Supporting Member Lifetime Supporter

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    Perish the thought! Never lubricate the packing!

    Do you put oil on your tires? Why no, you want it to grip...not slip.
     
  6. LoEM_1942

    LoEM_1942 New Member

    12
    4
    Lady Lake
    Gotcha! Still learning.

    In that case it seems like the packing is doing well. :D