Posted 02 January 2013 - 12:10 AM
I recently purchased a used KWA USP on the cheap that I knew was having some dry firing issues. It chronos well, and only fired dry every other shot towards the end of the magazine so long as it is warm.
My friend also ended up with a used USP for dirt cheap, and his is exactly as mine, except that his slide lock sheared from the slide release, so it won't lock either way. (Part #141 on his gun is missing the notch that holds the slide in place when it is pushed up by the magazine when empty)
So while looking to fix them both, this is what I noticed:
-The gun fired more dry shots (just gas no bb's) when the magazine was colder.
-The slide would not cycle completely, leading to no bb's being fed by Part #135.
-Leaving a cold mag to warm with the same amount of gas would cycle the gun entirely, ambient temperature mostly irrelevant (80F same as 65F, just warms faster).
-ONLY ON MY FRIEND'S GUN: Multiple bb's being loaded but no gas firing, then randomly a few bb's flying out of the barrel (happens when pointing the gun down too).
What I have done so far for my gun:
-Have NOT adjusted the hop up to turn it off, noticed that in my gun and my friends, the hop up holds the bb's in place well.
-Tightened screw #117 into Part #38/153 leading to rubber part #49 rubbing up on cylinder part #135. I put some lube to smooth it out, and the return springs aren't strong enough to pull it back, but I figured the gun sliding back will be enough to put it into place for testing only (I know, when you're out of bullets and the slide locks, the cylinder will remain open)
-TLC according to the GBB maintenance videos on this site's forums.
-Lined up the rocket valve #7 with the cylinder #135 on my gun (my friend's gun might be shooting multiples due to a misaligned valve, I'll dry the rubber on both off so they don't move around and I'll align them and retest).
What I think might be the issues:
I'm testing with three different mags in both guns, and I have swapped the slides and bottoms to no avail, so I think it might be:
1. The hammer spring might be weak on both guns, leading to less gas being used when the mag's valve starts to jam up.
2. The stock slide return springs are too powerful (my KWA M9 has a much weaker slide action and works wonderfully, these might draw way too much gas leading to a huge cooldown)
3. The Part #7 and #135 misalignment issue mentioned above.
4. The magazines aren't riding right up to the bottom of #135 leading to excess gas being released before the hammer lets off from the slide action. (bad design in other words, but just guessing as someone here mentioned using a CS style hand cup action to push the mag up, haven't tested yet, just a guess).
The lube I use is thick stuff with a very similar consistency to KWA oil:
Please help, I would deeply appreciate it. Also, please refer to the diagram as I obviously don't know the names of the parts.
Posted 03 January 2013 - 09:40 PM
Posted 04 January 2013 - 11:35 AM
GBB guns will perform their greatest when the temperature is warm. When it gets too cold, the magazines will freeze up, and performance will decrease. I'm sure you already know that.
Try not to put any silicon oil near the hop up bucking (part 37). Putting silicon oil on that rubber hop up bucking will cause it swell, and would lead to jams, where the pistol would fire and the slide will blowback, but no bb fired. Then, bbs will come out of the end of the barrel if you point the pistol down, or have too many bbs inside the hop up bucking. On that note, try not to lubricate any area where the bb touches. This includes the bb channel, the bb follower, the cylinder (in your case part 135) and the hop up bucking (37). Getting bbs covered in dirt/grime/silicon oil will only decrease performance. You can buy a new hop up bucking, or try soaking the bucking over night in soapy water to see if it helps...
Cleaning and maintaining the magazine is also a good idea. Be sure to disassemble the bb follower, follower spring, base plate etc, and get a Q-tip and run it along the bb channel to collect any grime. You talked about a misalignment from the rubber gas release port to the cylinder. I would lubricate that piece of rubber, as well as the gas release valve itself.
You can replace the slide stop lever/slide release lever by going to kwa's online pro shop and placing an order: store.kwausa.com
or, by calling KWA and buying the parts over the phone. Sometimes, the pro shop doesn't carry everything you need, or isn't always updated. KWA's phone number is 626-581-1777, open mon-fri 8:30 am to 5:30 pm PST, closed weekends and holidays.
If the gun is not cycling a bb into the chamber, it has to be the feeding arm that rides (and is connected to) the cylinder, part 135 on your linked diagram. The gun isn't shooting the bb because either:
a: the hop up bucking has swelled from too much lubrication and therefore is stopping the bb from moving,
b: the feeding arm that's connected to the cylinder is not shaped perfectly and isn't pushing the bb from the magazine into the chamber,
c: the magazine follower is too weak to push the bbs up the magazine's bb channel to the feed lips,
d: there may be grime in the magazine bb channel not allowing the bbs to slide upwards to the feed lips,
e: the bb follower is locked to the bottom of the magazine.
I can get a better sense of your problem if you upload a picture of the cylinder (part 135) by itself, focusing on the feeding arm underneath. If it is misshaped, it would definitely lead to your firing issue.
Posted 05 January 2013 - 08:39 PM
Thanks for the welcome and the reply, and a detailed one at that. I only bumped early on because I drove to KWA and it is a bit far from me, so I hoped for a reply before I left (I missed yours by a bit unfortunately).
I will clean out the three mags and lube the valve and the piece of rubber near the lip (mag gas outlet port?) and test further. The mags and followers do appear to be working well however, but worst case scenario, I maintain my mags so I'll do it.
I did put some silicone inside Part #135 but I cleaned it out so the Part #7's (valve) rubber head would stay put on #48 to address that alignment issue people mentioned with #135's outlet and #7. Aside from that, I have never lubed the hop up bucking; however since the guns are used, they could be swollen. I can try to soak them in soapy water, but prior to doing that, can I get some information on to just how much soap I should use, or what type of soaps I should avoid? I've never removed the hop up on any gun before, is there a guide somewhere as well? (or at least if it's simple and common sense guided let me know).
I definitely understand the cold issue, and I have tested the guns further and saw it in action (I'll explain). After realigning #7 and #135 for both guns, I found that my friend's performed better than mine, leading me to believe that the #7/#135 alignment is only a performance issue that is exaggerated by the true issue holding the guns back. I say this because after two mags of about 2 rounds every 3 seconds, the gun began to dry feed, and wouldn't feed properly for about 15 mins after that (only when the gun was warm, not the mags). This is inconsistent with my experience with properly working GBB's, which do have trouble when VERY cold but not when used at the rate I used them (which is strenuous I admit).
I can try to realign #7 and #135 in my gun, but I feel like it is only a half fix; just making the gun more efficient and therefore covering the problem for a bit longer (I'll do this anyway cause who doesn't like efficiency anyway?).
I do feel like the big problem is the #135 and and mag gas outlet port (rubber piece on top) aren't aligning or sealing properly. I checked that #135 goes back entirely on it's own (without the barrel pushing it back) and it does for both guns. I couldn't see if that was too far a movement since it's really hard to see if the slide's rubber port and the cylinder's port are aligned; but I assume since it is going back all the way, that is the aligned spot. In that case, it appears the seal is the issue.
This is of course ignoring that the hop up bucking or the feeding arm on #135 aren't the case. The feeding arm may not be the case because pulling the slide back (even half way) leads to many bb's loading. Plus, the gun, when missing shots, may also fire multiple bb's or just one. Both feeding arms (and feeding ramps) are nearly exactly similar, but I will post a picture to be sure. The hop up bucking being swollen however may be the case exactly. I do see excess gas being released from the slide while firing as the gun cools, leading me to believe that too much gas is going to the back of #135 just before the bb overcomes the friction from the bucking. The gun does chrono well though, but I have always chrono'd warm, so it could be that the first shot just does well.
Sorry for the wall of text and the thinking aloud, I figure the more info the more you can make of it. To summarize, it seems these might be the issues:
1. Hop up bucking
2. Feeding arm on #135 or ramp
3. Rubber outlet on magazine not seated with #135 for each shot
I will take pictures of both feeding arms as soon as it's morning since lighting is poor in my room. Thanks again for your help Outlaw!
Posted 05 January 2013 - 10:39 PM
So when you pull the slide back, do the bbs just come out of the mag? I'm thinking your magazines feed lips aren't holding the bbs correctly. Maybe that's why the gun may fire multiple bbs.
Whenever you get the chance, please upload pics of the feeding arm and feed lips.
I've used dish washing detergent to wash the hop up bucking... lots of it. I soaked one in a regular sized poland spring bottle overnight, making sure to shake the bottle and get foam/soap all over the bucking. Then in the morning I went back in with a q-tip to dry it off and clean off any excess grime. If that doesn't work, there are always extra hop up buckings on the kwa pro shop:
For removal of the hop up bucking. Remove the inner barrel (with hop up assembly) from the outer barrel. Punch out part 45 (pin). Remove part 145. Unscrew part 120. Remove part 36. Unscrew part 116. Remove part 146 (inner barrel clamp). Push inner barrel inwards so the muzzle end is going into the hop up assembly, then remove part 13 (c-clip). Slowly twist off part 12, being careful to catch the little hop up ball, (part 126), and finally remove part 37 (the hop up bucking). Do everything in reverse to reassemble. If you need literal instructions, I can always provide them for you.
Edited by Outlaw1995, 05 January 2013 - 10:45 PM.
Posted 05 January 2013 - 10:40 PM
Posted 08 January 2013 - 01:25 AM
So I took apart both guns, cleaned out the buckings (which were not in like-new shape) and soaked them. After test firing, I got similar results with my gun and a slight increase in performance in my friend's gun.
I did notice, however, that my bucking had silicon in the actual rubber, so lo and behold, after swapping the buckings, my gun performed considerably better. It appears then that both buckings have soaked silicon irreversibly and I could get them swapped out. I will of course only test one and see if it works.
I did put silicon on the outlet port of the magazine to swell it, but I can't really tell if it helped; I'm sure it didn't hinder anything.
As for the pictures of Part#135, I noticed my friend's part and mine were identical so I only took pictures of one:
I do want to ask for more literal instruction regarding the flat part of the bucking's location relative to Part#12, I tried to follow it in the picture as best as possible but I'm not sure how much it affects the hop up action.
Additionally, should #36 push up on the bucking or push against it? When it is pushing against it (in the same direction as the barrel), #36 doesn't screw in entirely, so I wondered...
Thanks for your help Outlaw, sorry for the hasty email, I'm very sleepy and it's late, so it's a bit here and there.
Posted 21 January 2013 - 08:13 PM
Posted 07 February 2013 - 07:40 PM
If anyone has any input other than a bucking, I'd appreciate your help.
Posted 09 February 2013 - 05:58 AM
The weak point in all magazine fed guns, real or airsoft, is the magazine. Double feeds, no feeds, are typical magazine problems. Solutions start with the cartridge/BB (are they in spec), mag springs, and mag feed lips. In gas guns is there sufficient gas in the magazine? Once those are eliminated as problems the feeding mechanism in the gun is the next suspect. The bucking is unique to airsoft but chamber problems are present in cartridge guns.
The trouble shooting possibilities seem endless but eliminate the magazines first. They're expendable albeit expensive in gas guns. For most hobbyists (us!) it's quicker and safer to send the pistol in for service. For starters KWA has the skills and parts.
PS: The Beretta trigger spring works perfectly in the KWA M9 pistol and is a common gunstore part.
Also tagged with one or more of these keywords: Slide, USP, Dry, Firing, Not, Locking, BBs, No
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