KJW M4

[weekenny]

Quick test 10 0.2's vs 10 0.25's.

 

Tested indoors using 2 mags from the weekend that still had gas in them. For accurate fps testing I'd have gassed the mags and waited between shots but this was purely a quick "vs" test for weights.

 

I'll do proper fully gassed mags 0.2's vs 0.25's vs 0.3's hopefully at the weekend.

 

Anyways todays result

 

0.2 Average over 10 - 310.9fps

 

0.25 Average over 10 - 301.2fps

 

well below the 30fps difference I'd come to expect from AEG's. Roll on the proper tests.

[t_hum]

Without freshly topped off mags the tests could be skewed. Though your results seem pretty consistent.

[weekenny]

Yeah the mag was topped off when I did the first test the other day. Today was just a quick trial as I didn't have propane handy. Not the most accurate test but interesting results none the less. The engineer in me is looking forward to the weekend when I can do proper testing but initial results mirror those of the other day.

[Leshy]

Does anone know how much a new cylinder is, the "feeding cue" that pushes the bb from the mag to the barrel has snapped off. Not even a month old and only one skirmish played, FS!

[t_hum]

First Ive ever heard of that part breaking. Shouldn't be an expensive part.

[tome]

Hi,

 

I'm getting erratic full-auto I read that some others have experience this but couldn't find a solution. The symptom is that it will fire 3-4 rounds fine then stop with the hammer forward. Using Green gas at the mo. Has anyone managed to find a way to rectify this?

 

Cheers

[t_hum]

This has been discussed quite a few times now but I don't recall which post #'s have the solution. It has to do with one of the following:

 

1. Sticky/slow moving mag valves.

2. The orientation of the spring connected to the full auto sear.

 

What happens after than 3rd or 4th shot. Does the gas vent from the mag?

[tome]

I've checked the valves on the back of the mags and they're quick to return. I'm not sure about the auto sear spring though. Is there a picture that shows how it's meant to be?

[t_hum]

I dont have one.

 

As to that last question I asked though... When the gun stops firing what happens? Do you rack the handle and get another three shots or so off? Or does the gun not cycle?

 

As stupid as it may seem I saw someone with this issue that was using a can nearly out of gas.

[Leshy]

I think a new cylinder is about $10 the price list is on the back of the manual and i'm going to assume its in TWD, I'll ley you know if I get a reply from kjw.

[tome]

When it stops I can rack the handle and get another few shots off at a good rate of fire. My can isn't new but i can still feel some liquid propane sloshing around in there.

 

I tried to see if the BCG was not engaging the auto-sear by taking the mag out, racking the handle, switching to auto, pulling the trigger and then racking the handle. It succedes in dropping the hammer every time the bolt returns to the forward position :-S

[t_hum]

So I assume this is a gas delivery or cycling issue. Do you have any aftermarket parts installed? Does the piston cup move freely over the piston and seal?

[tome]

Thanks for all the help man

 

I bought this from another member on arnies so i'll tell what i can see. There's one of your pistons in there and your velocity reducer. All other parts appear to be stock. The piston is free to move over the seal.

 

When it stops it does so very suddenly, it doesn't appear to have any sign of weak blowback before it stops.

[t_hum]

is the piston ring lubricated?

[tome]

Yeah, I gave it a spray of airsoft silicon lube and rubbed it into the o-ring before i stored it about a week and a half ago. Wasn't too sparing with the stuff either.

[t_hum]

Ive had terrible luck with spray lubes. The o-rings should be lubed with silicone grease only. The sprays get blown away quickly due to the tapered piston cup design as well as into the hop. If you can't feel a slick layer of grease on the inside of the cup Id get some grease on it. At the very least itll remove a sticky piston ring from the problem solving equation. At best, itll solve your woes.

[tome]

Ok i'll try silicon grease. The same stuff that I would use on an AEG piston head right? I'll give it a go tomorrow, a bit late here to be shooting full auto with the KJ being as loud as it is. The neighbours upstairs will complain

[t_hum]

Yeah. any 100% silicone grease is good.

[DesertFox]

Almost done, just a couple pieces left.

 

[Shadow_Ocelot]

What made you decide to put the QD sling mount behind your AFG? Why not on the side, either instead or or near your rail cover?

[DesertFox]

I tried it on the side, and it stuck out a little too much. It would sometimes hit my arm if I have my arm extended out straight. Seems like it won't get in the way if I stick it behind the vfg.

[Mental Medic]

That makes sense. Thanks man.

 

 

Reporting back on the whole "dial affecting hop direction" theory. After I stabilized the hop arm to prevent sideways movement, I tried a few mags. The result was the same as before: radical hooking to the right. I don't think it's the hop dial making the shots go right. I'll post how I stabilized the arm in a bit after I get some pics.

 

 

[Shadow_Ocelot]

If anyone has uppers with all the do-dads in them (i.e. hop unit dial, dust cover, etc.) with broken tabs I'd be up for taking them off your hands!

 

I want to get one of the plastic uppers to write up a review for us U.S.A. turds that can't have metal ones shipped, but don't have all the little extra parts. Anyone willing to let one go for cheeps, let me know!

 

(I know this isn't a BST section, but I figured it was easier to get straight to the KJ users here. If it's not supposed to be here, feel free to delete this mods.)

[johnyew]

Almost done, just a couple pieces left.

 

 

Nice setup!! I'm digging the UBR! I hope you did not go the 'difficult' route installing it as I have.

 

How did you install it?

 

Thanks.

 

ETA: Which version MOE grip did you use? Was it a simple plug and play install? Thanks.

Edited October 20, 2010 by johnyew

[weekenny]

I have the gbb version of the MOE grip and fitment is tight but it does go. Retain your original bolt though as its longer than the one supplied with the grip.