|
|
Post by honestjohn on Aug 6, 2022 18:00:56 GMT
So just as I’m getting back into a bit of pistol action after a lengthy lay off, my favourite auto a H&K USP has died on me mid shoot. Shot the first mag of 8 ok then on the second load it fired a couple then did not blow back. Thumbing the hammer back I fired another shot and that also did not blowback. Now the hammer will fall but no gas at all is released. I tried a different magazine thinking to eliminate the valves and seals in the mag, but the second mag was the same, no gas release when the trigger is pulled. I did a quick field strip and one bb fell out from somewhere where it shouldn’t have been,but the fault is still there. Clearly a further strip down is required. Does anyone have any suggestions what could be the issue with this gun?
|
|
|
|
Post by HeadHunter on Aug 6, 2022 20:45:06 GMT
I'm going to guess that an errant BB has got lodged inside the rocket nozzle of the blowback unit. I'd take a look inside the nozzle with a torch to see if it's there, as that would stop the blowback unit from working, as for the hammer not falling, that may be caused by either another errant BB lodged inside of the trigger's lock work or maybe the BB that appeared when you field stripped it may have caused some damage to the hammer disconnect or it could of moved/damaged something internally within the safety switch system. If you field strip the gun down again, just check the function of the safety switch, make sure that it's moving the right parts when you operate it, as the USP has a fairly unique safety system that the replicas copied almost identically from the real steel version. Have a look inside the rocket nozzle, if it does have a BB stuck in there you might be able to remove it with a strong-ish magnet rather than stripping the whole unit down and whilst the gun is stripped down, see if the hammer functions correctly before re-assembling it all, as this will help to diagnose the problem if you haven't managed to sort it from a strip down. I hope that helps John  If not, just tell us what happened and we'll have another 'crack' at it buddy..... |
|
|
|
Post by honestjohn on Aug 6, 2022 21:16:38 GMT
Thanks for that Shawn. I would hope to have a more in depth look at this either tomorrow or Monday. I was using the excite copper covered lead bbs in this gun as it has performed well with these in the past and I don’t get any ricochet issues in my indoor range, - so the rare earth magnet fix is a non starter. I haven’t got the very familiar memory of the innards of this gun (or any others for that matter) so I need to have it in front of me. However, thinking this through, I’m thinking that perhaps a rogue bb has got into the mechanism and is preventing the hammer striking the gas valve. If a lesser amount of gas was released before it stopped firing 5his could presumably prevented a full blowback. The trigger cycles and releases the hammer on the back of the gun but as you are aware this is not the hammer that is doing 5he business and is there for realism. All will be revealed, watch this space!
|
|
|
|
Post by honestjohn on Aug 8, 2022 21:48:28 GMT
Well some progress but no resolution. There are no rogue bbs in the mechanism, or inside the blowback unit. I have however made some progress. ![]()  Close to the heart of the problem seems to be the points I have marked 1 and 2. 2 is a sort of butterfly spring that rocks or at least controls the firing pin that the hammer strikes. 1 can move downwards and moves firing pin into a position that it can strike the release valve. Presumably this up and down movement of “1” is controlled by the slide. When the slide is in place of course you can’t see what is going on. If I cock the hammer and depress “1” and pull the trigger it all works. If I don’t release this lever it will vent all the gas.I’m wondering if there is a wear or mal fitting issue here. just had a light bulb moment! I posses an endoscope that I could insert up the pistol grip where the mag fits and hopefully I may be able to see what is or is not working when the slide is fitted. The gun is nearly working and it must be some sort of adjustment or misalignment. Any suggestions would be useful, and il dig out my endoscope tomorrow and see if that shows anything. |
|
|
|
Post by HeadHunter on Aug 9, 2022 0:49:40 GMT
Sounds to me like, #1 is the trigger disconnect/reset (to stop it from going full auto from one trigger depress) and #2 is the actual safety. Without looking inside the slide to see the clearances for #1 it's hard to determine if it's working correctly. One good thing though, the hammer is working as it should when the slide is off, so logically if you refit the slide and the hammer doesn't function then you know that it's a slide issue rather than anything else.
I'd have a good look inside the slide, especially at the clearance area for #1, see if there's any obstructions or fouling of the track way.
|
|
|
|
Post by honestjohn on Aug 9, 2022 15:03:19 GMT
Endoscope didn’t reveal much. I really needed more hands to hold things still. Looking in from the back of the gun I can see as the slide is slid onto position, the lever I marked at “1” is little depressed when it is ready to fire. The firing pin when struck by the hammer will not strike the valve unless this lever “1” is pretty much fully depressed. I tried to glue a piece of metal onto the appropriate part of the slide so as to depress the lever but that didn’t work as I think the metal needed to be thicker, the tiny piece of stainless I cut was only 47thou thick. I feel a bit like I’m trying to engineer it to work rather than find the fault that made it fail.
whilst I was racking the slide to test the thing, the long spring and guide has popped out o& the blowback unit and the spring has got mashed!! The pistol is now dead until I can find some blowback spares. I found spares of these parts for my 1911 a couple of years ago and it may be the same unit, but I can’t find them on line now. My pistol is dead for the foreseeable.
|
|
Doyley83
Bounty Hunter
Helpful member and Share holder.
Posts: 3,442
Likes: 4,170
|
Post by Doyley83 on Aug 9, 2022 15:24:09 GMT
Not sure if it's of any help at all but here are some pics of the metal components from my USP which is pretty much new -    The pistol is cocked in these pictures. If there is anything else I can do to assist with comparisons let me know |
|
|
|
Post by honestjohn on Aug 9, 2022 18:06:18 GMT
Doyley83, thanks so much for that. I can see from your photos right away that the “bent like a hair pin” type spring, that I think I previously called a butterfly spring towards the back is very much more aggressively holding up the ‘firing pin’ that the hammer strikes I’m going to see if I can bend my spring into the same sort of position that yours is in. It’s not easy because you can’t get at it, but looking at yours I recon it’s a prime suspect as it’s the sort of thing that could wear over time and perhaps slowly bring on my fault. Ther is a cross pin at the bottom of the butt that looks like it holds the hammer spring, and perhaps more. I’m thinking that a large part of the bits I can’t get at might withdraw through the bottom of the butt if I take this out. I’m building up to that, but unless I can source a new long thin spring and the pin from the end that fits in the blowback unit, I’m screwed. I know I’ve seen complete blowback units including these parts on line from an air soft supplier but I’m damned if I can find them now. The ones I’ve seen were for a 1911 but I recon they would probably be the same ones.
|
|
