KJW M4

[Andrew12]

Will they ship uppers to the UK? Anyone know?

 

If they did I could forward some on to the US.

 

Email clare and ask. If they will, i'll be glad to throw some business your way.

[Roman!]

Email clare and ask. If they will, i'll be glad to throw some business your way.

 

I would be willing to do the same. Otherwise I guess I will have to buy a plastic upper and keep that around as the backup spare. Meanwhile, I am just going to be very cautious every time I open up the body.

[Andrew12]

I would be willing to do the same. Otherwise I guess I will have to buy a plastic upper and keep that around as the backup spare. Meanwhile, I am just going to be very cautious every time I open up the body.

 

When removing the upper, instead of opening the rear and then the front, loosen the rear a bit, keep the body together and loosen the front. the lift the pieces apart.,

[Roman!]

Andrew, that sounds like a VERY good idea. The less stress the better on what is so far the one design flaw in this airsoft gun. Thanks for the suggestion!

Edited October 14, 2010 by Roman!

[weekenny]

I'll email claire when I get home from work and see if I can get a price for some uppers.

 

Out of interest does anyone have the weight of a "naked" upper so I can get a shipping cost for the US.

[johnyew]

Added teh UBR stock to my KJ. It involved a disc grinder, steady hands and most importantly, safety goggles as the chips were flying everywhere!!

 

 

Fully collapsed

 

Fully extended

 

 

It's not completed yet as I still need to cut the cheekpiece to fit the buffer tube and tap an M6 threaded hole for the UBR buffer tube locking screw.

[weekenny]

Ok e-mail sent to get a quote for Part #1 Upper Receiver, I'll update with the cost.

 

I've to mod a friends hop so I'll weigh an empty upper when I do that and go from there. Hopefully will be able to help some of you guys across the pond with replacement uppers.

[GingaNinga]

I finally managed to pull the hop-up arm out and coated it with a layer of shrink wrap.

After putting it back into the body, I was able to get hop-up, but their is still some trouble.

 

The BBs are now all curving to the right. I am guessing this might be an issue with the shrink wrap. Maybe it isn't an even spread.

The only thing I have noticed, and it was like this before I did the shrink wrap fix as well, is that the hop-up dial doesn't seem to engage the hop-up arm for the first 5 positions on the dial. Between the 5th and 6th position it comes almost completely on.

I wonder if this is the same for everyone.

 

I am thinking if ordering another hop-up assembly to see if that will help.

 

I was really looking forward to T-Hum's bigger hop-up arm

[t_hum]

The problem with the larger arm is it didnt really solve the problem. What bb weight are you using dstole?

[DesertFox]

Wasn't the shrink wrap mod essentially the same as a larger arm.

 

T_Hum maybe you can make a different spacer for the hop-up dial, one that's shorter than the original spacer with the ability to add small shims to fine tune the height essentially how much the hop up dial makes the hop up arm adjust.

[Mental Medic]

I finally managed to pull the hop-up arm out and coated it with a layer of shrink wrap.

After putting it back into the body, I was able to get hop-up, but their is still some trouble.

 

The BBs are now all curving to the right. I am guessing this might be an issue with the shrink wrap. Maybe it isn't an even spread.

The only thing I have noticed, and it was like this before I did the shrink wrap fix as well, is that the hop-up dial doesn't seem to engage the hop-up arm for the first 5 positions on the dial. Between the 5th and 6th position it comes almost completely on.

I wonder if this is the same for everyone.

 

I am thinking if ordering another hop-up assembly to see if that will help.

 

I was really looking forward to T-Hum's bigger hop-up arm

 

 

My shots are curving to the right too. It's been doing that ever since I've had it. Disassembly after disassembly, my shots hook to the right a lot. The problem I think, as t-hum has also found out, may lie elsewhere in the hop unit. But where......

 

[t_hum]

In our testing the actual size and travel of the arm, while insufficient in the current design, wasn't the only problem. The looseness of the arm and its propensity to move left and right during adjustment was also a big part of the overall problem. The issue I see from removing that spacer and adding one of a shorter length is that the dial would collide with the receiver where there is currently a little recess cut. For someone who wants to give that a shot though, shouldnt be hard to put some washers in there instead of the stock plastic spacer.

 

I would do it myself but Ive got a few orders to attend to in my "free" time.

 

Quick edit: Think about it this way... as you turn the dial it puts a side load on the hop arm. That means the arm moves to one side and creates an off-axis spin on the bb. Hence the hooking...

Edited October 15, 2010 by t_hum

[Mental Medic]

Quick edit: Think about it this way... as you turn the dial it puts a side load on the hop arm. That means the arm moves to one side and creates an off-axis spin on the bb. Hence the hooking...

 

That makes sense. Thanks man.

[DesertFox]

In our testing the actual size and travel of the arm, while insufficient in the current design, wasn't the only problem. The looseness of the arm and its propensity to move left and right during adjustment was also a big part of the overall problem. The issue I see from removing that spacer and adding one of a shorter length is that the dial would collide with the receiver where there is currently a little recess cut. For someone who wants to give that a shot though, shouldnt be hard to put some washers in there instead of the stock plastic spacer.

 

I would do it myself but Ive got a few orders to attend to in my "free" time.

 

Quick edit: Think about it this way... as you turn the dial it puts a side load on the hop arm. That means the arm moves to one side and creates an off-axis spin on the bb. Hence the hooking...

 

Yeah the only thing I can forsee is the screw that holds in the hop up dial may have to be shorten or spacers would have to used in between the Screw & Hop Up Dial, I just hope it doesn't interfere with the Bolt Carrier Group

[GingaNinga]

T-Hum

I was using .25 with HFC gas.

It is difficult to get BBs much heavier than this. The new .28 BBs from TM are available, but very expensive.

I guess I could give them a go though.

 

Man I want to get this sorted. I love the look and feel of this gun, but I just can't get it to be as accurate as i would like

[weekenny]

the hop-up dial doesn't seem to engage the hop-up arm for the first 5 positions on the dial. Between the 5th and 6th position it comes almost completely on.

 

 

Did you make sure the hop arm was free to swing within the part it fits with?

 

 

If there is too much wrap it will stick and the dial will not engage properly. I had this problem first go at it.

 

Also the two bits that the arm swings between had quite a bit of casting flash on them that I had to remove. This could be interfering with some hop arms giving a hook.

[GingaNinga]

Weekenny

Thanks for the photo.

I did make sure that the arm could swing freely.

Maybe the shrink wrap didn't shrink evenly.

 

Will try again

[GingaNinga]

Dp

Edited October 15, 2010 by dstole

[DesertFox]

So I modified my hop up by using washers instead of the regular spacer and so far I've been able to achieve some good hop up effect. However after around 3 mags for some reason my BBs didn't hop anymore. I took it down and checked it still seems like everything looked normal. Anyways it shows some good promise, but definitely requires more testing which I can't really do right now.

 

Only negative so far is that it makes hop up adjustment a pain in the *albatross*, since the wheel no longer turns anymore. You have to take it down unscrew the wheel and adjust by hand to the desired setting and screw in the screw that secures the hop up dial.

[weekenny]

Question about how the KJ Works see what I did there :unsure: lol

 

Anyway on to the question I fitted velocity reducers to mine and a friends KJ's and took them down to 300 - 315fps tested with 0.2's to make sure they were well under a tight 330fps for CQB games. Both tested for fps indoors so warm say 18C, then at site on Sunday chilly outdoor woodland site we got hit for random chrono and got 300 and 315 respectively. Spot on we thought at went on playing thing is we were (and this is where it gets interesting.... I promise) we were both using 0.25's.......... Now with my testing of AEG's I've seen roughly 30 fps between 0.2's and 0.25's back to back same chrono, so I thought damn need to adjust both guns again thinking they would be 330 - 345. Then today doing checks with 0.2's I was getting 315 on mine again, so I back to back tested 0.2's and 0.25's and I get only the couple of fps variation you'd expect shot to shot on a chrono.

 

Anyone else out there with a chrono care to do some tests as I think I'm going mad. Please back to back test 0.2's and 0.25's and post your findings. Thanks.

 

I think I'll do a mixed mag next time I'm testing and see if I can tell the 0.2's from the 0.25's may also stick a mix through my AEG just to confirm.

[suicidalsnowman]

From a theoretical standpoint, a heavier bb in a gas gun should see a reasonable fps increase since it stays in the barrel for longer and has more energy imparted on it from the expanding gas in the barrel.

[Shadow_Ocelot]

From a theoretical standpoint, a heavier bb in a gas gun should see a reasonable fps increase since it stays in the barrel for longer and has more energy imparted on it from the expanding gas in the barrel.

 

Maybe that FPS increase, combined with the added weight of the BB countered each other, and that's why you got the same readings with the two different weights

 

Try instead of doing a mix doing a full magazine of each, and film videos for the rest of us! What combination of spacers did you use for CQB?

[weekenny]

From a theoretical standpoint, a heavier bb in a gas gun should see a reasonable fps increase since it stays in the barrel for longer and has more energy imparted on it from the expanding gas in the barrel.

 

Perhaps, never seen a pistol do that though, but perhaps the short barrel hides the effect.

 

 

Maybe that FPS increase, combined with the added weight of the BB countered each other, and that's why you got the same readings with the two different weights

 

Try instead of doing a mix doing a full magazine of each, and film videos for the rest of us! What combination of spacers did you use for CQB?

 

 

Could be I'll try some 0.3's from my mates sniper if I get the chance. Don't have a way to video two mags but could note the fps for each and post that.

 

I used the thickest and a slightly thinned down middle one. I found a thick and thin was about 345 and a thick and middle was about 285 so I took a little of a middle sized one and did trial and error testing. Hence one gun ended up ~315 and the other ~300. Testing combined with trial and error seems to be the best method as I seemed to get much higher fps than t-hum was reporting for the spacer sizes.

[t_hum]

The thing about the general chart I posted is that is very environment dependent. A few degrees, differing humidity, etc. all play into the final reading.

[weekenny]

The thing about the general chart I posted is that is very environment dependent. A few degrees, differing humidity, etc. all play into the final reading.

 

Very true. Thats why I suggested trial and error to get the desired fps.

 

Whats your view on the consistent fps across bb weights?