KJW M4

[PianoBlack]

Has anybody here tried to install MAGPUL's BAD Level or a ready-mag system? I haven't heard from the seller in my last AEG transaction since he confirmed he received the payment last weekend so paypal might be getting a dispute and I may be getting a KJ.

 

-Piano

[t_hum]

Raven1 has installed and uses both. They both work well. I'm

sure he can field specific questions.

[Rookie Ab]

The BAD lever ,fits like a glove and works perfect.

 

My Redi-Mag is a real steel and has to be 20 years old.It works with my WA mags but is not deep enough to engage the catch and retain my KJ mags.

 

If the newer ones fit the KJ mags,guess I'll have to buy another.

Edited December 4, 2009 by Rookie Ab

[t_hum]

I believe Raven1's is actually a Classic Army model and engaged the mags very well.

[Raven1]

Has anybody here tried to install MAGPUL's BAD Level or a ready-mag system? I haven't heard from the seller in my last AEG transaction since he confirmed he received the payment last weekend so paypal might be getting a dispute and I may be getting a KJ.

 

-Piano

 

 

Confirmed, Please refer to post #941 on page 48 of this thread and you'll see examples on both primary and reaction side of the gun.

 

Both work as expected and have had zero issues due to the weapon be used as configured.

[PianoBlack]

Thanks Raven1. *****

 

-Piano

Edited December 5, 2009 by PianoBlack

[Raven1]

Friday, December 2nd, 2009

 

1600 Hours

Temperature 62F / 16.6C In Sunny Arizona

 

Propane Gas Used - Coleman Propane Fuel - http://www.thegreathardwarestore.com/Produ...&click=2744

 

Firing Mode Rapid Fire Semi Auto Only - Semi Auto Only!

 

All Magazines Rapid/Semi Auto Fire 10 Shot Control Groups

 

Gun State:

 

Magpul B.A.D. Lever - Cradle Airsoft Piston - Cradle Airsoft Aluminum Velocity Reducer - Blown Lower/No Buffer Retaining Pin To Provide Strain Relief to BCG - Cradle Airsoft Lower Solution - Using 'Echo 1' .25 BBs

 

Again - This Is A Blown Lower - Gun Operating As Expected - No Change In Gas Efficiency or Hop Up Operation

 

Commenced Testing:

 

Ran the gun in rapid semi auto fire and the gun ran as expected. Responsive, quick cycles, consistent BB grouping at 25 yard CQB engagement distance.

 

Magazine 7 - 8 Issue Encountered

 

Noted Gas Efficiency Declining on Magazine 7 as only 2 reload were achieved on 1 gas fill. Magazine 8 demonstrated a large exhausting of gas throw the brass ejection port on shots 1, 2 and 3; once shot 30 was expended the magazine gas fill had been depleted. Disassembled the gun and found the lower solution had rotated in the back of the carrier. Where the lower is blown out there is a sharp edge / corner and was striking the carrier as it cycled into the buffer tube.

 

Please Note: The carrier has over 11,000 rounds of wear and the constant impact from the cycles has 'enlarged' the inside diameter of the rear of the carrier. The lower solution was made from the dimension of an entirely new carrier and therefore the fitment hold is tighter. This is a 'Beta' prototype (IE: the first of its kind) and will go through several iterations until a final design is completed

 

Adjustment made to the lower solution and reinstalled then repositioned into carrier.

 

Post Lower Solution Adjustment Objective - Demonstrate Non Venting Of Majority Of Gas Reservoir In Beginning Shots Of Magazine

 

Filled Both Magazines with gas - loaded both with 32 BBs - 1st, 2nd, 3rd Shot of Both Magazines Slow and Controlled.

 

1st shot fired demonstrated normal, responsive, quick cycling cycle of the BCG - Noted No Gas Venting

2nd shot fired demonstrated normal, responsive, quick cycling cycle of the BCG - Noted No Gas Venting

3rd shot fired demonstrated normal, responsive, quick cycling cycle of the BCG - Noted No Gas Venting

 

Remaining shots expended rapid semi auto fire - Both Magazines

 

Loaded Magazines with 32 BBs each

 

Both Magazines expended rapid semi auto fire,

Both Magazines expended rapid semi auto fire,

 

Both magazines exhibited gas depletion on 3rd BB reload on shot 22 and shot 24 - Bolt locked back on every occasion INCLUDING when magazines exhibited rapid gas depletion.

 

3 BB reloads per gas fill. Average for these magazines on this gun

 

!!Test Objective Success Achieved and Concluded!!

 

 

Post Script/

 

Having spent an extreme amount of time learning and understanding the Tanio Kobayashi gas system I have garnered a true respect and dare I say 'Admiration' for Kobayashi-san's competency in fluid dynamics. The buffer retaining pin is the shape it to guide the carrier into the buffer tube - True. Also the buffer retaining pin pulls double duty in of the fact that it also keeps the carrier from rotating. Keeping the alignment of the BCG Flat and Directly Over the Magazine Seal. Which is why Snoopy found Full Auto Fire Performance with a blown lower inconsistent at best. There is simply too much linear and rotational forces being exerted on the BCG group during full auto cycling with the buffer pin guide not present for reliable full auto fire.

 

Tanio Kobayashi-sans design allows for the carrier to act independently from the bolt cup as the front of the carrier or the cup is moving linear on the guide rod, then pulled back onto the carrier in conjunction with the band and spring. The carrier works in conjunction with the buffer retaining pin as its 'Guide' to keep it alinged with the magazine seal and into the buffer tube as well. Every component is well thought out with purpose and efficiency. As the gun was developed for Japan it was designed with the operating constraint of Duster gas. Which is why during Kobayashi-sans pre-production testing blown lowers were never encountered. The lower solution t_hum developed keeps the buffer from EVER striking the buffer retaining pin. Allowing the pin to perform its true function of keeping the back of the BCG inline. But rest assured, there are other enhancements in the works to address the Only Real Flaw or Chink in the Armor of this weapons platform,,,

 

 

 

Total Magazines Expended Today = 18

 

3 BB Reloads To 1 Gas Fill

 

Total Issues / Incidents Encountered = 1

 

Total Bolt Locking Back After Last BB = 18

 

Total Magazine BBs Expended = 576

 

Total Round Count = 11,456

 

[Speed=]

Hey can someone pm me or post here what the email is for KJW?

[MrTreble]

kjworks@ms47.hinet.net

 

If you are going to ask questions, it would be best to be short and concise. And use simple words. =)

[sacairsoftsn00py]

Raven1-

 

Did you replace your recoil buffer with the metal one?

 

I am thinking having a metal one would result in a quicker blown lower than if you still had the original delrin/plastic recoil buffer. Same goes with the upgraded harder recoil spring.

[Speed=]

Well guys I'm currently negotiating with a Hawaiian that would get me KJW M4 and 4 mags.

 

He says he hasn't used it much and the only problem he's had was that the hopup isn't effective at all. Says it's been that way since got it.

 

I'm hoping that all I need is to get a new rubber or something along those lines. But for those who own the KJW maybe you can throw me some advice or input. Thanks.

[t_hum]

Could possible be lube affecting his accuracy. Its hard to tell how well people treat or maintain their guns. I wouldnt worry.

 

 

Range Report:

 

Today Raven1 and I got together for some accuracy testing and compared the stock KJW barrel to a TB.

 

Testing conditions:

48 deg F.

Propane

.25g Echo 1 BBs

Shots were made in a supported position.

Range was 20m

Each round was 10 BBs

 

Stock KJW results:

Round 1: Overall grouping size is approximately 8 inches with the majority of shots within a 6 inch circle.

Round 2: Overall grouping size is approximately 8 inches with the majority of shots within a 6 inch circle.

 

KJW with 6.03mm M4 length TB barrel:

Round 1: Overall grouping size is approximately 4 inches with the majority of shots within a dime sized circle.

Round 2. Overall grouping size is approximately 4 inches with the majority of shots within a 1.5" circle.

 

FPS was not measured using a chronograph but deductive reasoning on both of our parts estimates the TB adds approximately 20 FPS.

 

 

[Speed=]

sounds phenominal. Good luck with the rest of your process t hum. I hope to buy from you soon!

[MunkyMo]

In installed my Cradleairsoft parts today.

Installation went smoothly for both the velocity reducer and the piston. Simply amazing how easy the change was, also amazed by how practical working inside this gas gun was. I've had a Tanaka m700, several WA pistols and a KWA mp7. All of those have a million small parts that I'm relatively certain dissolve when in contact with air and require at least 5 hands to re-assemble.

Very pleased with my results. I live in KY, USA. Right now the temperature is ~36 degrees F, or 2-3 Celsius. I gassed the mags, didn't allow them to warm at all and slapped them in. I was able to get an entire mag out on full auto, and ~60 shots on semi rapidly tapped out. No noticeable change in range/FPS from the first to last shot. The recoil was suffering though.

One finicky thing: My bolt wasn't locking back on the last shot, but I have a feeling that's because the BCG didn't completely cycle due to reduced recoil. I didn't put any spacers on the velocity reducer, just the o-ring. I don't have a chrono to give quantitative results.

 

Eagerly looking forward to a TBB.

[SwatMP5man]

I have literally just got in from a night-ish game, temperature around 2-3 degrees celsius, and found that the mags vented after 1 round at this temperature, however after that i managed to keep 2 mags down my plate carrier to keep warm and successfully fired another 18 mags fully all night with duster gas.

 

Will give a combat report when i have installed t_hums parts next weekend.

Edited December 6, 2009 by SwatMP5man

[MunkyMo]

It wasn't allowing me to edit, but I was using Propane.

 

In the cold, I recommend using Propane, no matter what. And make sure your mags are probably greased, my round follower wasn't coming up occassionally.

[t_hum]

Good to hear install went smoothly. Remember to keep your o-ring lubed well. In really cold temps I've found the lube helps as the rings can sometimes harden up slightly during long auto bursts.

[MunkyMo]

Still having trouble with the lock-back. Any suggestions?

 

Also, I've noticed my bb follower seems to stick. Since you can't work the spring in the traditional method (pushing the loading rod up and down into the magazine) anyone have any good methods for lubing and loosening the spring/follower?

[MrTreble]

Some of the newer magazines made by KJW had weak springs. You'll want to contact KJW and get some new magazine springs.

[Speed=]

And f I recall you'd have to preform the takedown on the mags and you could use a spacer or iIm ay have just came up with that from some other forum. lol

[t_hum]

As far as the locking back question:

 

1. Do you have the new buffer and buffer spring from KJW? This only applies if your gun has a serial number on the mag well. Some say these parts help with reliability of the bolt stop function.

2. At near freezing temps your recoil is going to suffer as the propane will not expand as rapidly. Cold temps + cooldown = ocassional failure to lock back. AFAIK, there isnt a whole lot we can do at this point to combat this given the very nature of using propane as a propellant.

[Raven1]

Raven1-

 

Did you replace your recoil buffer with the metal one?

 

I am thinking having a metal one would result in a quicker blown lower than if you still had the original delrin/plastic recoil buffer. Same goes with the upgraded harder recoil spring.

 

Yes I did, but I prefer how the gun operates it this configuration.

 

Bolt cycles more smoothly and locks back every time than with just the stronger magazine spring alone,,,

[SwatMP5man]

Quick tip for anyone installing the piston and having problems getting the original off, no matter what tape i used or how much pressure i applied with pliers it wasn't moving. I ended up using a soldering iron going through the back of the BCG and slotting the tip into the allen key slot in the screw, left it there for 2-3 minutes (the whole BCG will become very hot!) and the screw came of much easier. I noted on mine that the whole screw was covered in orange gunge which i assume is locktite, must have been overdone in the factory.

[Hite]

Anyone know where I can pick this gun up from the UK? Can only find it in stock at ehobby asia.

[MDK_Marshal]

Special airsoft supplies seem to be the only retailer in the UK with it in stock (AFAIK), but I seem to recall hearing some not-so-great things about them in the past, so I'd be a bit hesitant to buy it from them...