We Katana GBBR Issues

[Bakasaur]

Hey Guys,

Recently acquired this gun in a trade. I was super excited.. except it's full of issues.
Basically - gun will fire semi auto perfectly fine. Full auto is a different story. It has difficulties feeding, the nozzle will get trapped in the hop up unit and the the bolt will move back and forth. Gas consumption is also horrible.

Here's a video:
https://www.youtube.com/watch?v=uABp...ature=youtu.be

Here is what I've done:
3 different bolts, 3 different trigger boxes (all combos) (From Ra-tech and We)

Different hop buckings (Ra-tech, Maple leaf, stock)

Machined nozzle to not make contact with the hop chamber (on the edges and feed ramp thing). Also modified the bottom of the nozzle to make minimal contact with the mag feed lip.

Modified the bolt for less resistance over trigger (Changed angle of ramp, polished to 0.5micron)

Modified bolt for less resistance over buffer spring retention pin thing. (The
little pin that holds the buffer in). Again, changed angle of ramp, polished to 0.5micron

Different weights of buffers and buffer springs

Different buffer bushings

Modified maglips for less resistance against nozzle

---------
I put brand new ratech parts in it, still had the issues. I've tested the parts in another we m4, it worked flawlessly. So I have no idea what's going on. I'm going to assume to receiver is out of spec. But I don't even know if that would be a possibility.

Guy I traded refuses to do anything about it. He told me it worked and it didn't. And rather than driving to Northbay to kick his ass, I'd like to figure this out.

Thanks,
Josh

[beta678]

You should be using semi anyways w/ a GBBR, that being said, bolt looks dry as fuck... try lubing it and the internals with some grease like ultraslick, should help it out a bit.

I know the WE CQBR M4's need to be lubed pretty well or you'll run into some issues, not sure about the raptors though.

[Bakasaur]

Thanks for your response,
It's been lubed and cleaned and relubed. Still has issues. I know I should be using semi-only, but the fact that auto doesnt work bothers me.

[beta678]

Hm... in that case, I recommend maybe heading over the gasgun.info forums and asking there. There's a dedicated WE GBBR section with a lot of guys who know their way around WE's.

PS. did you lube w/ oil or grease? I find Silicon oil does pretty much nothing for my GBBR's, need something heavier like grease, which stays in place to keep them properly lubed.

[Bakasaur]

I'll try as well, thanks!

I use ultraslick. It's the only good grease I find for GBBRs

[Kos-Mos]

That looks like your auto-sear is skipping/releasing too early.

Check the top of the auto sear. It should not be silver, only the the rear face tip should be.

If you have some closed-bolt auto sears, that will cause that kind of issues. Basically the hammer rides the bolt carrier and causes light strikes, just enough to push the bolt a bit back but not a sharp kick.

Your hammer can be worn/rounded too.
And before you say "it's all brand new", I had the same issue with brand new RATech steel components until I filed a sharp edge on the hammer and filed the auto-sear square (this part is stamped, so the edge is rounded a bit).

[Bakasaur]

Originally Posted by Kos-Mos

That looks like your auto-sear is skipping/releasing too early.

Check the top of the auto sear. It should not be silver, only the the rear face tip should be.

If you have some closed-bolt auto sears, that will cause that kind of issues. Basically the hammer rides the bolt carrier and causes light strikes, just enough to push the bolt a bit back but not a sharp kick.

Your hammer can be worn/rounded too.
And before you say "it's all brand new", I had the same issue with brand new RATech steel components until I filed a sharp edge on the hammer and filed the auto-sear square (this part is stamped, so the edge is rounded a bit).

Hey Kos, Thanks for the info. Do you think you could snap a photo of what they're supposed to look like? I don't wanna fuck it up and take off too much.

[Kos-Mos]

Well, it's kinda easy to see in fact. Put the gun in Auto, rack the bolt.
Press and hold the trigger, then rack the bolt slowly and ride it in. Then open your receviers. If you hammer is down, that is the issue. Remove a little bit (half a mm) and try until it's perfect.

As a queue, the closed-bolt tip is curved a bit, stamped end too. Open bolt is squarish (I guess they re-processed the ones they had, however mine is old, so don't go by that only).

[Bakasaur]

Originally Posted by Kos-Mos

Well, it's kinda easy to see in fact. Put the gun in Auto, rack the bolt.
Press and hold the trigger, then rack the bolt slowly and ride it in. Then open your receviers. If you hammer is down, that is the issue. Remove a little bit (half a mm) and try until it's perfect.

As a queue, the closed-bolt tip is curved a bit, stamped end too. Open bolt is squarish (I guess they re-processed the ones they had, however mine is old, so don't go by that only).

Remove a little bit from both parts, as you said earlier, or from the hammer or sear individually?

PS: Sear is open bolt. I chucked a brand new ra tech carrier/nozzle and trigger box in it.

[Kos-Mos]

Only from the tip of the auto-sear. That is the plate-like rocker that is at the rear most. It interfaces with the fire selector and hammer.

Especially if you dropped a complete trigger box in there. The ONLY difference between a "closed-bolt" and "open-bolt" trigger kit is the auto-sear that is shorter on the open-bolt.

RATech made the triggerbox a while ago, before the open-bolt. You might have a non-converted closed-bolt one.

[Kos-Mos]

Here:

Box inside the gun has been modified:



Box outside is a brand new drop-in from WE. It is labelled as "closed bolt" but the auto-sear drags on the bolt. You could see on the bolt that there are two section that are worn, the middle where the hammer interfaces and the side where the auto-sear is not supposed to touch but does.



The angled tip has to go on the "new" trigger box.

[Bakasaur]

Kos, I think you just saved my gun build.
I looked at the "new" trigger box. There's wear on the sear from it dragging on the bolt like you described. There is also a sharp angle, which shouldn't be there. Unfortunately I have to catch a flight tonight so I won't be able to fix it, but I believe that's definitely the problem.
Which leads to this in my excitement soon having a working gun:

THANK YOU, YOU WONDERFUL HUMAN.

[Trendkilla]

Same issues with the WE MSK