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KJW M4

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Beware of RATech's silicone o-rings. They cause nothing but problems in the WA system because they are too soft and absorb too much oil.

 

If you want to upgrade your KJW, stick with Cradle Airsoft's robust design.

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Clean the inner barrel/hop bucking (before and in between skirmishes or whenever possible)

 

lube the Cradle o-ring piston (use silicone grease or the like and you won't need to do it frequently)

 

spray some silicone oil into the output valve if they feel sticky (wont happen if you use green gas)

 

those are the main things to keep in mind...

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Ra-techs basic concept here is ok I guess. Its basically an x-ring which is what I include with the pistons now in addition to the standard o-rings. However, I cannot understand why they continuously spec silicon o-rings. They have terrible propane chemical compatibility (rated as "poor" by almost every chart Ive read) and are NEVER to be used in dynamic sealing applications.

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To bring in a lot of WA user experience with RATech silicone O-rings here:

Their fit starts out fine. As you use the gun more and more, the o-ring expands and gets tacky. Pretty soon, what was a good sealing low friction piston becomes sticky and sluggish. This can happen really, really fast, in as little as a magazine worth of firing.

 

If you ever frequent the GGI forums, and you search for RA Tech or RATech o-ring you'll see that just about everyone who has bought an item with an RATech o-ring has had this problem. Some people believe the solution is to buy more of the $2 RATech o-rings. Others believe that using a material with chemical resistance is the answer.

 

RATech knows about the problem with their material choice, they choose to ignore it. It's a shame because they constantly provide good concepts but fumble the execution.

 

In this situation, there's no reason go with their product.

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I finally installed the Cradle Airsoft o-ring piston and made the simple shrink wrap tube mod for the hopup. I cut about 5-7 mm lenght piece of the shrink wrap tube and placed two layers of it in the hopup arm. I used lighter to shrink-fit it perfectly. The hopup unit was quite easy to dismantle and to put it back together (didn't even need any guides). Also found a small 1.5mm hex screw from my boxes, and finally got the front sight tightened properly.

 

All good so far.

 

Now that I tried shooting through the window towards the forest, I could actually give over hop to my 0.28g BB's as well as low, and when in right setting, the bb's fly incredible(!) distance straight on, as watched through my SpecterDR. What's most amazing to me, is the consistency of the shots. No flyers and every shot hopped just about the same amount. My power setting is around 117m/s (384fps) with 0.28g bb's (about 2 joules which is below the limits for semiautomatics, as I play with semi), so the range is quite phenomenal...

 

This gun will definitely dominate the battlefield! Super-duper thanks to everyone here at Arnies!

Edited by Lupus78

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Hi guys, I need help! I have had problems with my KJW M4's range from the day I've purchased it. First I thought that my hopup bucking was oily from using a green gas that has too much silicon oil in it. I've cleaned hopup bucking with alcohol to remove any oil but range was not improved. The range is very similar regardless which BBs I'm using (0.28g or 0.25g). BBs fly strait for 20m and then drop down like a rock.

 

I did notice that my hopup lever is moving very little when I turn the hopup wheel but have noting to compare with to be sure that's the problem. Hopup chamber is very simple and I don't think it causes troubles.

 

My KJW M4 setup:

- Cradle airsoft piston

- Cradle airsoft velocity reducer with no spacers

- Cradle airsoft carrier extension

- Cradle airsoft 6.03 TBB 363mm

 

Any suggestions what to do? Please, I'm desperate :(

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Open the receiver, take out the BCG, and look down the barrel as you adjust the hop up to see if it's doing anything.

 

Even with zero hop, you should be getting more than 20 meters. What kind of conditions are you in?

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When the hopup is turned on completely the range is slightly increased but still it's way to low according to what other users here on Arnie's have.

 

Today was more than 30°C (86F) so that shouldn't be the problem. Maybe the hopup lever is not moving enough so the hopup effect is too low.

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You could do what other members have recommended -- covering the hop up arm with shrink wrap, so that it has more effect.

 

Look a few posts above for information regarding it.

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That's exactly the reason why I just tried the shrink wrap tube mod for my hop up. Look it up from this thread! Even with maximum setting the bb's flew like 20-30 meters and dropped fast after that. Now after the mod I can adjust it to shoot straight all the way, or even over hopup if I wanted to. (Two last settings will shoot up in the sky.)

 

I used two layers of shrink wrap tube, just as there was a picture here in this thread.

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That's exactly the reason why I just tried the shrink wrap tube mod for my hop up. Look it up from this thread! Even with maximum setting the bb's flew like 20-30 meters and dropped fast after that. Now after the mod I can adjust it to shoot straight all the way, or even over hopup if I wanted to. (Two last settings will shoot up in the sky.)

 

I used two layers of shrink wrap tube, just as there was a picture here in this thread.

 

Was there a picture? What page is it on?

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Was there a picture? What page is it on?

Here you go...

 

Got an answer from Clare finally. I just paid the parts. It seems that the belts and hopup buckings cost around $6 a piece and bolt stop about $9 each. Ordered enough of those so I won't run out of spare parts any time soon.

Edited by Lupus78

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An alternative to the bolt carrier extension fix to save the lower receiver

 

 

After taking apart the buffer tube assembly, I noticed that the rear area of the bold carrier sticks a little farther than the detent pin for the recoil buffer. So I thought, how can I have it set up so the recoil buffer does not slam into the detent pin and destroy part of the lower receiver.

 

Previously, the only solution offered was by purchasing a bolt carrier extension (pushes the recoil buffer back by a couple of millimeters so it doesn't slam into the detent pin).

 

I have found that you can shave down the detent pin's rear by an mm or two (so the recoil buffer sits farther up front). What this does is that when the upper receiver is closed, it is the bolt carrier's back that pushes the recoil buffer's head back (and away from the detent pin). The key here is that the the recoil buffer's head will not be slamming into the detent pin (which was the purpose of the bolt carrier extension)

 

With bolt carrier extension however you end up with a heavier bolt carrier group which then results in a heavier recoil. This works well in conjunction with green gas.

 

If you are using duster gas however, a lighter bolt is better to have for better gas efficiency and function. The lighter your bolt carrier group is, the quicker it blows back.

 

I have been using the PC duster from Walmart and get power in the neighborhood of 360 FPS with .20g BBs...the higher the temperature is, the higher the pressure of duster gas is (which in turn results in higher FPS readings).

 

My KJW M4 CQBR is bone stock in terms of parts with a couple of modifications done to it using a Dremel (cut off disks and sanding bits), sand paper, and metal polish.

 

So far its held up just fine...Even the piston cup is holding up fine. I'll keep the new KJW M4 CQBR for summer use (with duster gas) and will keep my old KJW M4 (converted to CQBR) for use in the winter with green gas.

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@Lupus78

Thanks bro. You save me some trouble searching over the whole thread :) I'll try that as soon as I get back from business trip. Can't wait!

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Initial Impressions: This this is amazing, i've shot a lot of aeg's in my time and this gun is fun. I've also fired a we scar gbb and the recoil is slightly less, but you can barely tell.

 

When I first got the gun, the stock, and the front grips were rediculously wobbly, some well placed electrical tape fixed that right up. I shot the gun stock roughly about 300 rounds with propane, without lube in the gun. Bad idea, during the installation of t_hum's tbb, bolt extension, o-ring piston, and muzzle reducer, i had noticed the original piston seal has already broke. Not to worry installed all the new stuff and now the gun is amazing!!!

 

I've actually shot 90 rounds with 1 propane refill, temp is about 70 degrees!

 

I emailed claire regarding the sling mount for the cqb version and have yet to get a response, hopefully i'll hear from her soon.

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Only thing that's slightly odd with my gun, is that full auto works pretty erratic if I don't press the magazine with the other hand. It's like the valve isn't pressed fully by the hammer, or the seal between mag and nozzle is too loose. There's a small (one or two mm) wobble there. With semiauto it works smooth enough, even without pressing. Auto-sear and the trigger group looks fine and I wouldn't even think that's the problem, since when I push the mag, the full-auto works 100% fine.

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I think someone solved this a few pages back. Something to do with the sear spring being out of position if I recall correctly. Look back over the last 7-10 pages or so.

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Travis -- got your parts! The gun fires so great now! I had to take out the weight in the BCG to put in the extension, but the blowback seems crisper now, anyway. The piston went in really easily, and I can already tell a difference in consistency -- thanks so much!

 

I also got the TRX and PEQ15:

 

CIMG9164.jpg

 

What do you guys think? I've got a Troy rear sight, KAC TT-brake, and Millett DMS-1 on the way.

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