KJW M4

[Hut73]

I thought I'd make a video of just some of the problems I've been having with my gun, and what I think is the source of all the malfunctions, which is the amount of bolt carrier wobble. Can anyone with a properly functioning gun tell me how much wobble is normal?

 

http://youtu.be/oHJNFWAJFnQ

 

Just checked a v1 and a v2 on mine and I don't think that's the problem... V2 looks to be just as "wobbly" as yours is. V1 not quite so much... Beyond that, not sure I could tell you what the issue is without closer inspection...

[D2D]

Just checked a v1 and a v2 on mine and I don't think that's the problem... V2 looks to be just as "wobbly" as yours is. V1 not quite so much... Beyond that, not sure I could tell you what the issue is without closer inspection...

The thing is, if I shim the upper receiver so as to lessen the horizontal play of the bolt carrier, the dust cover and bolt catch start to function as they should. The failure to go into battery problem is still there, presumably because I haven't eliminated the vertical play of the bolt carrier.

 

Here's an addendum video, showing the play between the guide rod and the bolt carrier:

http://www.youtube.com/watch?v=fEFGN0zL704

[Valkyne]

@D2D - Your experiences are the exact reason why I swapped back to the V1. My V2 seemed to just bang up everything inside both upper and lower receivers, causing more wear than I felt was necessary.

[D2D]

I would if I could, but I assume KJW doesn't sell v1 parts anymore. IF I'm right about the source of all my problems, then I figure I'll just get another v2 bolt from KJW or hold out for t_hum's bolt. I'm really hoping that I'm right and that it's not some dimensional problem with the upper receiver or something...

 

So with that said, can anyone please check their v2 bolts, like in the addendum video? It'll only take a minute.

 

Also; I don't know why I didn't do this sooner, but I did some measuring with my calipers. The diameter of the guide rod is 4 mm, and the uh... Guide rod hole, doesn't seem to be perfectly round. It's about 4.20 mm ± 0.03

Edited April 23, 2012 by D2D

[JackAAA]

D2D, Are you using the v2 bolt with a new ver. bolt catch and a new ver. buffer?

[Jackster802]

I'm already regretting trading mine away. If anybody finds a steal on one let me know. I really want one

[D2D]

 

D2D, Are you using the v2 bolt with a new ver. bolt catch and a new ver. buffer?

Yes. I bought it new as a v2.

[Cj Radge]

Hi D2D. I did the exact test shown in your videos. I have pretty much the same play in your first video and addendum video. I also use digital caliper, results: guide rod 4mm. guide rod hole 4.15 ( only 0.5 difference from yours but not sure if that is enough to cause your problem).

 

Mine is working flawlessly though.

 

I noticed two unusual:

1. Your plastic bolt head seems to have more play than mine.

2. For the bolt lock, your bolt carrier was unusually more forwarded exposed. It should be more backward when locked. Mine is only exposing 10mm of bolt carrier. (note: bolt carrier only, Plastic bolt was not included in the 10mm measuremet)

 

Hope it helps isolate the problem.

Edited April 24, 2012 by Cj Radge

[Leshy]

Did you all have a good weekend rocking your kjw m4s'?

 

I tried a KSC M4 yesterday, Ive had my eye on one of these for a while and I wasnt Impressed the recoil felt "springy" was this a lemon or has anyone else had the same issue? I know this is a KJW forum and this isint trolling, I'm just interested im your opinion.

 

T-hum any news on that BCG, the money is burning a whole in my pocket.

[johnyew]

Weekenny,

 

How is your diy TDC mod holding up?

 

I had gone through your previous post again and will probably perform the mod based on your instructions.

 

Also, any thoughts of having the set screw contacting/touching the hop up directly instead of through the arm or is that not possible due to space constraints.

 

Thanks.

Edited May 2, 2012 by johnyew

[weekenny]

It's holding up great on both mine and my team mates rifles. I haven't adjusted mine since the day I set it up.

 

The set screw has to push the arm as to have it push on the rubber it'd have to be a bit further forward in the upper and it would need to be spot on. As you can see in my post my test on a spare upper was a bit off but it still pushed the arm fine and it didn't kick off to the side but had it been on to the rubber it'd have been too far out.

 

Also if you have any rough or uneven facing on your set screw it could damage the rubber.

 

The arm is much more stable with a screw pushing it so there is no reason to omit it.

[johnyew]

Thanks.

[D2D]

t_hum, could you perhaps reduce the price of shipping to Canada? $14 to ship such a small part like the velocity reducer seems a bit much.

[t_hum]

I'd love to. Problem is I don't make a penny on shipping. The prices on the website are my prices from USPS. UPS charges you guys insane brokerage fees so that's out. The only other option is for me to ship things in different packaging, hand fill out all the info as opposed to their online tools and then I'd have to lie every shipment and say they're not commercial goods.

 

The first chance we get to ship more cheaply and pass the savings on, we will.

 

Edit: Looks like I lose 1.75 on every Canada shipment, actually.

Edited May 4, 2012 by t_hum

[D2D]

Oh well, it was worth a try. I'll still be ordering one. Interesting, though - it's $14 whether I order 1 or 100.

 

Will the velocity reducer work with your new bolt carrier?

Edited May 4, 2012 by D2D

[t_hum]

We use flat rate shipping so anything under I think 30 lbs is the same price.

 

Yes, it will be compatible.

[Darkstrike]

I can't find the edit button, so I'll just double post.

 

I have discovered an interesting malfunction while playing with my fix mentioned above. If the wedge is just slightly too thick, the bolt will release itself automatically as soon as a new magazine is inserted.

 

iv had this problem too!! happens with my kj 1911 too for some reason? any info on how to fix this? id like to be able to press the bolt release when i put a new mag in rather then have the gun do it for me! silly gun...

[Ivan Mabatan]

im sure it will, but i figure id ask. im assuming the cradle velocity reducer will work with my ra-tech bcg?

[yellowjournalism]

Anybody think an Angry Gun 300% buffer would work in a KJW?

[freon]

Stuff I've recently learned from my KJW:

• The accuracy of the stock barrel vs an edgi 370mm 6.00 tight barrel that I had made is no comparison. Stock 6.03 barrel is better
  
• Having a barrel longer than 370mm will not increase fps unless you increase the hammer spring tension. This has to do with the amount of gas expanding inside the barrel, too little and the bb decelerates before it leaves the barrel.
  
• If you tighten the hopup and do the shrink-wrap mod then the hop should be fine.
  
• black bbs are awesome when your gun is zeroed.
  

So my gun is back to stock except for the external modifications done (mk18 mod 1) and I am scoring consistent headshots from 50 to 75 meters on people looking out from their cover and trying to find me by tracing my shots. I'm using a V2 bolt but want to go back to a V1 and will soon.

[Leshy]

I have used .43 blacks, what joule are you using to get them out to 75 meters?

[Kai_Wolf]

Likewise, I plan to get away from a v2 bolt. Hopefully, the new BCG will prove to be as good as the v1 or better! I cant wait to start using my kjw again. Freon, the stock kjw barrel is the very short one, yes?

[freon]

Kai, yes, the stock barrel is the 270mm one or the short one. I'm going to experiment with having a 6.03, 365mm madbull barrel modified to fit and see how that turns out.

 

Leshy:

I'm running .32 bbs on green gas/propane, which brings the gun's power to about 450 to 500 fps depending on the days temperature. On hotter days my bbs tend to curve up a little in flight but not nothing drastic. On cooler days it becomes harder to get the bbs out to 75 without aiming a little higher than your target.

 

At some sites I have to lower my gun's power so I switch to 134A. Without adjusting the hop, my max effective range is reduced to 50m but it's still just as accurate.

 

As for bb weights and range, the heavier the bb, the farther your effective range up to a certain point. If you use bbs that are too heavy for the power of your gun then your range will suffer. It's the same thing if you use bbs that are too light because lighter bbs decelerate faster in flight. The trick is to find the goldilocks bb weight that is just right.

 

This is what I use personally:

sub 320 fps: I use .28s

320 fps to sub 450 fps I use .30 bbs

450 to about 500fps I use .36 bbs.

 

I recently found black .32bbs. They aren't branded or anything so I wouldn't be able to tell you how to get them but I'm having a good time using them in the 320 to 500 fps range.

 

Of course, none of the above information will matter if your hopup isn't configured properly. Instead of shrink wrap for the hop mod, I used small strips of duct tape.

 

Please note that the gun's power output will affect the max range of your gun while the weight of the bbs will determine the effective range of your gun.

Edited May 10, 2012 by freon

[Kai_Wolf]

Well it seems that my V bolt really isnt coming through as time goes on. From time to time, I will get nothing out of a full magazine, just the triggler click. I thought it was my magazines until I put a v1 bolt back in. I noticed after a while that my shots were slower and less crisp. I got used to it thinking it was normal until I tried a Cradle Airsoft v1 back into my gun and BAM, it shot like a champ. I made this video the other day and you can see me using it in the "All Gassed Up" portion of our CBQ training. At the part I enter one of the rooms, my gun "clicks" on a full a loaded magazine, and thus I have to palm strike the target and transition. I cannot wait to get one of Thum's new bolts to fix this issue. I think it has an issue mainly with the O ring cup or something as a V1 bolt works swimmingly.

 

Note ARdrummer and Frogfish of Arnies are also in the vid.

 

I dont know if anyone else is having this issue or not.

 

[WTF?Shane]

I haven't played in months and used my KJW the other weekend. Seemed fine except for the bolt catch sticking issue when inserting magazines when the chamber is open. Firing seemed fine until my bolt return spring broke.

 

Edit: Sick video, Kai_Wolf!

Edited May 15, 2012 by WTF?Shane