Pts mkm horrid clicking noise

[REX3446]

Hi, I'm new here, and this is a last resort because no one will help me, pts doesn't respond and nether does my local shop. Now the problem is when ever I charge the bolt to load in a mag, the bolt gets stuck right at the last bit, so I have to use the forward assist. And when I do it makes a horrid click. Also this ONLY happens when the gun is in auto mode, when in semi it's fine. I really am stumped.

[Rock-climby-Dave]

something in the trigger group is sitting a bit proud on full auto. double check all of the sears aren't broken or bent. Check the very front and rear of the BCG to make sure there are no burrs on it.

 

Has it always done it or developed the issue over time?

[REX3446]

It's only started doing it since I got a hpa mag. I think it might have bent it with some of the sustained fire I have been doing.

[Rock-climby-Dave]

Compare your trigger and bolt carrier groups to another (new, or not broken) and see if there are any irregularities.

[REX3446]

I just had a long look at one on google and my one, they look identical! Although, it could be that it's such a small difference I'm not able to identify it.

[proffrink]

Check the surfaces within the trigger group like Dave says - is there any part where there's more wear (i.e. it's shiny rather than the dim anodised colour)?

[REX3446]

The only place that looks worn out is the part that catches the bolt when the mag is empty, and I cleaned all round there, and that's not the problem. As I said, only in auto it does this l, but when it's up it looks a bit bent. But I'm to sure if it is supposed to be. Thanks for everyone's help.

[proffrink]

The fact that it's doing it in full auto suggests a trigger mechanism or sear issue - nothing else changes position from semi to auto as you could imagine. As Dave says, it's possibly holding the hammer too high and it's grinding against the bolt.

 

What is it that looks bent? The hammer? Bent to one side or not sitting at a 90^o angle? On most airsoft designs it never goes 90^o except in the moment you pull the trigger as there's a small spring in where the valve knocker is that pushes it back (without this you'd vent the whole mag).

 

The magazine catch shouldn't be an issue as it would cause problems in both semi and auto if it was sitting too high - this is easy to test anyway as it's not engaged until your last shot anyway so it's removed from the equation when your magazine is full. Again, any issues with the mag catch would appear on semi too so you can basically rule that out.

 

This it almost certainly a problem with the trigger mech or hammer. You may notice that the hammer is held at a slightly different angle by the sear when it automatic (you may need to reset the hammer twice to observe this difference. As such, I'd look at your trigger sears too (located underneath the hammer). This could be the culprit as they wear quickly. If you're using an HPA tapped magazine, you absolutely should be investing in proper steal parts as bits wear down.

 

Edit

Finally, check your full-auto sear towards the rear of the lower (silver bit) as these are known to wear down all the time. Buying a steel one isn't much money (£7-10), but they are a little fiddly to replace. Can you send us a picture of it all?

[REX3446]

I'll send a picture, I just need to get on my computer. Thanks for everyone's help!

[REX3446]

This is what it looks like

[proffrink]

From above please. Also, use imgur.com to upload and post images - easier on the server.

[REX3446]

http://imgur.com/a/ciHiv

[proffrink]

Edit (questions)

1. When you charge it for the first time and the bolt doesn't go fully forward, once you've mashed the forward assist a bit is the hammer still cocked and ready to fire? Does the same issue happen when firing or just on the first shot?

 

2. If you charge it on semi then switch to full auto and fire do you have any issues?

 

3. If you charge it on semi then switch to full auto and cycle the bolt again, do you have any issues?

 

4. Please raise the hammer (i.e. pull the trigger) and then point your camera down into the lower and look towards the part I've put an arrow indicating (keep reading and you'll see why that bit is important) as I need to see the bottom of it as it may be deformed:

 

 

Nothing appears out of the ordinary from your pics, but obviously the trigger sears and the bottom of the full auto sear are concealed.

 

It's very hard to diagnose such a problem without being able to see the sears (but that means a full disassembly), however I've seen this happen in an LM4 before (functionally identical design). The way the full auto sear works (bit on the left in that latest image you showed me) is it holds back the hammer slightly as the bolt reciprocates then allows it to drop again. If you're interested in the motion, then look up a real M4 as the mechanics are the same and indeed the full auto sear is identical.

 

Problem is, the hammer is meant to catch on the bottom of that there sear. You'll notice when you switch from semi to auto it rocks backwards in such a way that the bottom of that sear is now in the way of where the hammer would be during normal cycling. Like I was saying earlier, if you pull the trigger and reset the hammer manually you'll see it sits slightly differently in the lower than in semi.

 

All in all, that full auto sear takes a hit every time the bolt cycles as it holds the hammer back slightly so that it isn't released before the bolt carrier unit is back forward again. Basically, the stock ones get destroyed all the time. I'd advise removing the full auto sear to check the bottom (don't lose the C-clip that you have to remove from the pin to push it out). In the image below, it's circled in red (that's the bit that gets kicked a little every time you fire in full auto):

 

 

There's no other explanation for it really other than something seriously wrong with the formation of the hammer or bolt. I would advise getting an aftermarket one simply for longevity if you're using an HPA-tapped magazine, but I can't find one for the LM4 series - just for WA-based M4s. The WA ones should be fine, so I'll find the cheap steel one I bought if it turns out to be the problem.

 

Here's a video on how to get that sear back in:

[REX3446]

Thanks for all your help, but I just don't have the tech skills for this sort of thing, is there a place I can get it serviced by professionals?

 

Thanks!

[proffrink]

If you want professionals then try shooting off an e-mail to http://www.milspecsolutions.co.uk/

 

Thing is this may be as simply as swapping out that full auto sear - if that's the case I'd be happy to fit it for you for free; it's a 15 minute job and most, but if you could get that picture of the lower part of it we can see if that's really the issue or not. If it's something more complex then I'd suggest a professional of course because they've the parts on hand to fix it immediately most of the time.

 

Could you also answer the questions from my post if possible?

 

Or you could dive in yourself: GBBRs are hard to break permanently because there re no sensitive electronics - if you assemble it wrong it won't work until you reassemble it correctly, but equally it's very, very rare to fully break something that isn't just worn down through regular use. Sure you may end up with a pile of bits and have to watch an hour-long Youtube video on reassembly, but at the end of it all you have a knowledge of how your own gun works and can save a lot of money.

[REX3446]

1: yes, it is ready to fire, and after that all the shots seem normal, as there is a lot of force pushing the bolt.

 

2: no issues

 

3: yes it still gets stuck if it's already been charged

 

One thing o must mention, I pushed the hammer down manually on fully auto, and the trigger wouldn't do anything, like it was stuck until the small metal part was pushed forward ( the part you marked out with an arrow)

[REX3446]

Oh and when I pushed the marked metal bit it makes that exact clicking noise that I think is something being out of alignment. https://www.youtube.com/watch?v=WjjN9PBlz-8 i made a video so you can see.

[proffrink]

Yeh, it's the auto sear as you've just confirmed. When you push it forwards, it sits in the position it would for semi (i.e. disengaged), so that's why it works again. Usually the bolt would smack that sear forward like you are there, so that could be a culprit too.

 

Either it's damage to the surface of the hammer (not likely as I can kind of see it there) or it's misaligned - as you say - or just very worn. We kind of need to look at the bottom of the auto sear though as that's where it contacts the hammer. Finally, it's also possible some dirt has built up in your selector and is pushing the sear further than it should be.

 

So it could be a case of disassemble, clean and reassemble those two parts or - at worst - a new auto sear (just under £10). It's up to you if you want to try it yourself or get someone else to do it. I will say there are plenty of reassembly guides out there for the selector or and auto sear, but if you've not the time then it may be best to send it to some place like Milspec Solutions (though be ready to pay a fair amount of money).

 

I can't find anything on the compatibility of WA-compatible auto sears with LM4 designs. I'd say they should work, and at most may require a small bit of filing - this could be come a problem if you send it to a professional as not many will keep the OEM parts as specific as this in stock (indeed, I couldn't find anywhere selling an original sear other than the KWA website).

 

If it were me I'd remove the sear and check it for damage. At worst I'd have to replace it later (a little fiddly) and at best I can know where the problem is and then maybe sort out a replacement part myself rather then sending it to someone who's just going to tell you that they need to order the part in and that it's going to take weeks for that to happen. I'll see if I can find anything on WA parts compatibility (because if they work then that's a lot of effort saved). Without that sear the only effect you'll get is that obviously you'll be locked to semi only.

 

Basically: It's either the bolt not pushing that sear forwards when you shoot or the sear is worn or misaligned.

 

Edit

Could you take a picture of the underside of your bolt too?

[REX3446]

http://imgur.com/a/mUtfw

[proffrink]

Hm, see the thing is by design it won't fire with the sear back on auto anyway - the bolt has to knock it out of the way. Your bolt looks fine in those pictures, which still makes me thing the auto sear is to blame (though I can see some fair amount of wear to the hammer there too). Auto sear looks seated correctly, and though I still can't quite see the contact edge it doesn't look too bad.

 

I'm afraid one would have to get their hands on it to help further, so it's looking like you may have to send it off. Hopefully it's just a case of cleaning the lower and/or replacing the hammer and auto sear. Thing is, stock GBBRs aren't meant to last for ever and they're made cheap. That's the main issue I see with people using all these HPA magazines - huge amounts of wear on the internals.