Calling all KJW GBBR Doctors.

[Olisharpeye]

I have just returned from a CQB match at Flag Raiders during the match my KJW M4 stopped working. I've never seen anything like it. The bolt carrier is jammed in just a little before the bolt catch. It will absolutely not budge by the hand of god could not move it. I've removed both pins out of the lower receiver releasing it. I've checked everything up and down. Made sure it had proper lube and nothing blocking or clogging anything in the lower or upper. So I slapped it back together for it to jam instantly again the moment the charging handle is pulled. The odd part was this gun was operating just fine for the chrony and sighting/hop up adjustment. After putting it together for the second time it will now not even come apart even when both pins are removed from the lower. Carrier is stuck inside the buffer tube and I've tried to use a punch to knock it out but it will not budge.

I need help, as I would like to go again next Monday. I'm extremely desperate.

Thank-You for your time. I would post pictures but I don't think it will do much good. But I will if you think it will give you a solution.

[IggysPiggy]

Post me some pics for refference my KJW is in my lap

Edit.

If the bolts far enough back the recoil retaining pin may be locking it back(the piece that keeps the recoil piston from shooting out when you split the receiver) but that doesn't explain the initial issue...

[audi_bhoy]

That would be my first bet too. Look for the pin near the brass tube at the back of the lower body and see if it is worn, and if there is any scratches on the bolt as well.

Version 1 or 2 bolt do you have?

[Olisharpeye]

The KJW is Version 1(Rubber Band system) When I manage to pry this M4 apart I will post pictures that you both requested. Of the Bolt Carrier and Buffer retaining pin. Thank-You for the quick reply.

[Olisharpeye]

I quick took these shots. So I was able to pry the lower and upper apart by half a centimeter giving me enough room to see whats happeneing. The nub by the buffer tube doesn't seem to have anything to do with the jam. But the trigger sear does. The carrier is going over the trigger sear, I believe that's what it's called. The L looking device that hits the square bar that hits the magazine valve. but for some reason doesn't allow it to go back over. I'm guessing it has something to do with bolt extension.






Edit: So I've reslapped it back together. The same problem occurs. Everything is normally seated, when the charging handle is pulled back the bolt carrier extension gets caught on the trigger sear not allowing it to move forward. I don't know if my trigger sear is broken(not going down far enough) or if my carrier extension is worn out.

Edit#2: I've managed to reconstruct exactly what my problem is without the upper receiver blocking your view.

^
That is my issue. Any ideas how to fix it? Unfortunately I forget where the trigger sear used to sit, it looks the same to me. There is some wear on the bottom of the extension but it looks like average wear and tear.

Edit 3: So as I'm tinkering away and I have come across my exact problem. Hooray and shit. I was looking at reference photos of the KJW Bolt Carrier and noticed mine was missing a long piece that goes under piston. The gentleman using my rifle never told me that a piece had fallen out. I've managed to sand a bevel into the metal and it now cycles again, but I will be order a new bolt extention. I'd like to thank you two for the quick responses.

[daishi]

Get a version two bolt assembly. Clean your buffer tube. Replace the bolt catch with the one that comes with the new assembly. Mine was jamming alot and I just got a version two bolt and it never jammed again.

Version two bolt is like 48 bucks from kjw WITH shipping included and comes with the new bolt, bolt catch, buffer and spring.

[Zack The Ripper]

Originally Posted by daishi

Get a version two bolt assembly. Clean your buffer tube. Replace the bolt catch with the one that comes with the new assembly. Mine was jamming alot and I just got a version two bolt and it never jammed again.

Version two bolt is like 48 bucks from kjw WITH shipping included and comes with the new bolt, bolt catch, buffer and spring.

^This.

A friend of mine had a similar issue to yours, although not quite as severe (he was able to release the bolt every time, but would jam again every half mag or so). He bought the version 2 bolt and upgraded his charging handle (although I think the charging handle had little to do with it) and it works like a dream now. Feels a little crisper when it fires with the version 2 as well, or so he says.

[audi_bhoy]

From the pictures, I think that there is a metal tab missing under the plastic nozzle, can't find my complete V1 bolt but found an extra carrier and I'm pretty sure the tab sits under the nozzle.

This would make sense since the trigger hammer isn't supposed to leave the metal tab and sit on the nozzle.

So, get a version 2 bolt directly from KJW.

[Olisharpeye]

The V2 Bolt, is it fully assembled or just the housing and you have to put the piston, gas regulator and all that fun stuff into it. The reason I asked is I just priced out all the bits inside the bolt carrier except for the guide rod and charging handle. Also priced the buffer and magazine latch and the price came around 86 dollars CAD to buy directly from KJW.

[Brian McIlmoyle]

rusty springs.. rusty buffer tube? do you do anything to maintain this gun?

it's probably not working out of protest.

[McCrea]

The buffer tube is brass, it's not rusty...

[Brian McIlmoyle]

Originally Posted by McCrea

The buffer tube is brass, it's not rusty...

I stand corrected.. really , brass.. how about that.. carry on

[McCrea]

There is a inner buffer tube made of brass, the exterior is pot metal :P

[daishi]

Originally Posted by Olisharpeye

The V2 Bolt, is it fully assembled or just the housing and you have to put the piston, gas regulator and all that fun stuff into it. The reason I asked is I just priced out all the bits inside the bolt carrier except for the guide rod and charging handle. Also priced the buffer and magazine latch and the price came around 86 dollars CAD to buy directly from KJW.

The bolt is completely assembled and comes with everything I listed. I'm not sure if you would have to buy a new guide rod and charging handle tho since it doesn't use an elastic.

[audi_bhoy]

The V2 bolt comes ready to drop in, you will change the spring guide, the bolt lock and the bolt itself, these all come with the V2 bolt. You need your original bolt guide rod and charging handle. The V2 comes with the stock valve shooting 460ish fps though.