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KJW M4

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I have to say that I love this platform so much that I now own two KJW M4's.

 

One is serialized and the other is not. There are some definite differences between the two. I will do my best to explain what I have found so far.

 

Outer appearances are identical except for the end of the stock outer barrel being a lighter color on the non-serialized version. I didn't take any pictures because I don't think the difference is enough to show on the pic. Also, the hole exposing the mag release spring that I discovered in the magwell of my serialized gun is non existent in the other.

 

The BCG tells two different tales.

 

P3310261.jpg

 

P3310260.jpg

 

The BCG on top is the non-serialized version. As you can see they are identical except for the weight at the back of the serialized version.

 

P3310263.jpg

 

This weight definitely has an effect on ROF. The non-serialized version and unweighted BCG has a much higher ROF. You would think the weighted BCG would have more felt recoil but the opposite is true. Maybe because the cycle happens so much faster in the non-weighted BCG.

 

 

Now the pistons.

 

P3310264.jpg

 

Starting from the left is Cradle Airsoft's O-Ring Piston. In the middle is the stock piston from the serialized BCG. To the right is the stock piston in the non-serialized BCG. These pistons are all very different, but the clear winner is the Cradle for is longevity.

 

 

I will be installing TB barrrels in both this week. I did notice that the hop-up on the serialized version worked flawlessly where as the non-serialized version will probably need the shrink tube fix. I will take pictures once I get them both apart and see if there are any differences.

Edited by Phenom1

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<b>@Phenom</b><br><b><br></b><br>The absence of the weight in the Bolt Carrier group is to facilitate better full auto fire and help maintain gas efficiency as less gas is needed to complete a bolt cycle.<br><br><b>@senators2094</b><br><b><br></b><br>Those front sets should work fine and just bolt right on.  As a rule of thumb: if it is a quality AEG Front set then it will simply bolt right on with no fitment issues.  I am using the G&P Defender Front set on mine.<br><br>Using a free float rail will give you more consistent shot groups - Not Tighter but More Consistent<br>Using a tight bore inner barrel yields tighter shot groups with improved velocity and range.<br>Using a free float rail in conjunction with a tight bore barrel yields markedly improvement in consistency and tight grouping.<br>In a word - "Fantastic!"<br><br>My personal set up is:<br>G&P Defender front rail set<br>KJW Factory Barrel Machined down to 10.5" (this was done to keep the factory Hop Up at Stock Factory Configuration)<br>Cradle Airsoft Madbull V2 Tight Bore Inner Barrel<br>I have been very satisfied with the performance.<br><br><b>@</b><font color="#2B3730"><font face="arial, verdana, tahoma, sans-serif"><b>slipknot1971</b></font></font><br><font color="#2B3730"><font face="arial, verdana, tahoma, sans-serif"><b><br></b></font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">Yes - I am having my lower machined to fit a RS Buffer tube!</font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730"><br></font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">Yes - I am using a free float rail, I recommend them highly!</font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730"><br></font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">Truth be told I have a Great respect for the Engineering of the KJW/TK M4!</font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730"><br></font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">The more I learn / discover about the design of the gun the more impressed I am by the function and the simplicity of the design.  The simplicity of the design also plays heavily into the durability / reliability / accuracy of the platform.  You this very obvious by just disassembling the gun, looking at the quality of the parts.  Lets be honest, look at the hop up halves and how it is held onto the inner barrel.  The components are not the highest quality and yet the hop up working like magic!  Look at the plastic bolt and how well it loads the BBs into the hop At ANY Angle with out a mis feed or failure to load.  The gun; simply put,,,Just Works, it goes Boom when you need it to.  Lets you stay out in the field until You Break Down - Not the gun.  No other Platform Can Claim This Right Out Of the Box!  Not Right Out Of The Box - No Other Gun.  <b>What We Have Here Gentlemen Is The AK-47 of the GBBR World!  </b>The design isn't the prettiest or the most CNC'd; it just simply works.</font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730"><b><br></b></font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">Being a 'True' JDM (Japanese Domestic Market) product Tanio Kobayashi designed the gun for the Japanese Market.  That being said some design aspects of the gun were employed so that there is no possible way the gun could be fitted to fire actual rounds.  This ideology was designed into the buffer tube - again the gun runs great.  But I Absolutely Abhor the buffer tube!  My Magpul MILSPEC CTR Stock fits fine, as do most carbine stocks.  My personal preference is to have a stock mounted sling mount ( Magpul A.S.A.P. Plate or Similar Single Point Plate) on the gun.</font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730"><br></font></font><br><font color="#2B3730"><font face="arial, verdana, tahoma, sans-serif">I have no issue doing this as the guide rod in the charging handle keeps the BCG moving linear and flat.</font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">It is due to this guide rod that there is no "Yawing" or "Pitch" in the Y - Axis.  Due to the guide rod, the BCG can ONLY move linear away from battery and similarly back to full battery.  It is due to this guide rod that the carrier will strike / contact in the center of the buffer in the same place every time.  The critical point to make is that the Outside Diameter of the Buffer mate perfectly with the Inside Diameter of the buffer tube.  The carrier is simply the force driving the buffer - There Is No Friction Occurring Between The Carrier and the Buffer - Only Contact.</font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730"><br></font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">Tanio Kobayashi designed the buffer pin to act as a guide to keep any torsional / twisting movement of the BCG at zero in the X-Axis.  This is why it is Rectangular and Wide, look at the wear on the guide groove on the underside of the carrier.  When noting this you'll also note the carrier does not travel as far back into the buffer tube as one would think.</font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730"><br></font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">Which is why I am not at odds with attempting this mod.  Plus my personal preference is to use a 'Legacy' design buffer tube assembly.  Why?  The design is mature and has been proven, bought and paid for by the lives of the American service men and women over the last 40 years.  When it comes to weapons platforms there is No Bigger After market than the AR After Market.</font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730"><br></font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">Having said that, here is the work being performed:</font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730"><br></font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">  -- The Stock KJW M4 Metal Buffer Weighs 72 Grams  --</font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730"><br></font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">The brass inner buffer has been removed.</font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">The bore where the brass buffer connects has been drilled to a larger diameter using 1-1/8" Drill Bit,</font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730"><font size="2">The bore will be threaded to the proper size using a Stoner Tube Tap </font><font color="#000000"><font face="Arial"><font size="2">Tube Tap 1-3/16"-16 threads per inch,</font></font></font></font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">RS DPMS Castle Nut,</font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">RS DSA 6 Position Buffer Tube,</font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">RS Magpul A.S.A.P. Plate,</font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">Airsoft AABB Aluminum Speed Buffer (Machined to 72 Grams)</font></font><br><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">Airsoft AABB Summer Weight Spring (Since I Primarily Use Propane)</font></font>

 

<div><span class="Apple-style-span" style="font-family: arial, verdana, tahoma, sans-serif; color: rgb(43, 55, 48); "><br></span></div><div><span class="Apple-style-span" style="font-family: arial, verdana, tahoma, sans-serif; color: rgb(43, 55, 48); ">I will update a range report and document with plenty of pictures the work being done on the gun.</span></div><div><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730"><br></font></font></div><div><font face="arial, verdana, tahoma, sans-serif"><font color="#2B3730">If any are taking interest please stay tuned,,,</font></font></div>

Edited by Raven1

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@Phenom

The absence of the weight in the Bolt Carrier group is to facilitate better full auto fire and help maintain gas efficiency as less gas is needed to complete a bolt cycle.

 

@senators2094

Those front sets should work fine and just bolt right on. As a rule of thumb: if it is a quality AEG Front set then it will simply bolt right on with no fitment issues. I am using the G&P Defender Front set on mine.

 

Using a free float rail will give you more consistent shot groups - Not Tighter but More Consistent

Using a tight bore inner barrel yields tighter shot groups with improved velocity and range.

Using a free float rail in conjunction with a tight bore barrel yields markedly improvement in consistency and tight grouping.

In a word - "Fantastic!"

 

My personal set up is:

G&P Defender front rail set

KJW Factory Barrel Machined down to 10.5" (this was done to keep the factory Hop Up at Stock Factory Configuration)

Cradle Airsoft Madbull V2 Tight Bore Inner Barrel

I have been very satisfied with the performance.

 

@slipknot1971

Yes - I am having my lower machined to fit a RS Buffer tube!

Yes - I am using a free float rail, I recommend them highly!

Truth be told I have a Great respect for the Engineering of the KJW/TK M4!

The more I learn / discover about the design of the gun the more impressed I am by the function and the simplicity of the design. The simplicity of the design also plays heavily into the durability / reliability / accuracy of the platform. You this very obvious by just disassembling the gun, looking at the quality of the parts. Lets be honest, look at the hop up halves and how it is held onto the inner barrel. The components are not the highest quality and yet the hop up working like magic! Look at the plastic bolt and how well it loads the BBs into the hop At ANY Angle with out a mis feed or failure to load. The gun; simply put,,,Just Works, it goes Boom when you need it to. Lets you stay out in the field until You Break Down - Not the gun. No other Platform Can Claim This Right Out Of the Box! Not Right Out Of The Box - No Other Gun. What We Have Here Gentlemen Is The AK-47 of the GBBR World! The design isn't the prettiest or the most CNC'd; it just simply works.

Being a 'True' JDM (Japanese Domestic Market) product Tanio Kobayashi designed the gun for the Japanese Market. That being said some design aspects of the gun were employed so that there is no possible way the gun could be fitted to fire actual rounds. This ideology was designed into the buffer tube - again the gun runs great. But I Absolutely Abhor the buffer tube! My Magpul MILSPEC CTR Stock fits fine, as do most carbine stocks. My personal preference is to have a stock mounted sling mount ( Magpul A.S.A.P. Plate or Similar Single Point Plate) on the gun.

I have no issue doing this as the guide rod in the charging handle keeps the BCG moving linear and flat.

It is due to this guide rod that there is no "Yawing" or "Pitch" in the Y - Axis. Due to the guide rod, the BCG can ONLY move linear away from battery and similarly back to full battery. It is due to this guide rod that the carrier will strike / contact in the center of the buffer in the same place every time. The critical point to make is that the Outside Diameter of the Buffer mate perfectly with the Inside Diameter of the buffer tube. The carrier is simply the force driving the buffer - There Is No Friction Occurring Between The Carrier and the Buffer - Only Contact.

Tanio Kobayashi designed the buffer pin to act as a guide to keep any torsional / twisting movement of the BCG at zero in the X-Axis. This is why it is Rectangular and Wide, look at the wear on the guide groove on the underside of the carrier. When noting this you'll also note the carrier does not travel as far back into the buffer tube as one would think.

Which is why I am not at odds with attempting this mod. Plus my personal preference is to use a 'Legacy' design buffer tube assembly. Why? The design is mature and has been proven, bought and paid for by the lives of the American service men and women over the last 40 years. When it comes to weapons platforms there is No Bigger After market than the AR After Market.

Having said that, here is the work being performed:

-- The Stock KJW M4 Metal Buffer Weighs 72 Grams --

The brass inner buffer has been removed.

The bore where the brass buffer connects has been drilled to a larger diameter using 1-1/8" Drill Bit,

The bore will be threaded to the proper size using a Stoner Tube Tap Tube Tap 1-3/16"-16 threads per inch,

RS DPMS Castle Nut,

RS DSA 6 Position Buffer Tube,

RS Magpul A.S.A.P. Plate,

Airsoft AABB Aluminum Speed Buffer (Machined to 72 Grams)

Airsoft AABB Summer Weight Spring (Since I Primarily Use Propane)

I will update a range report and document with plenty of pictures the work being done on the gun.

If any are taking interest please stay tuned,,,

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thanks fellas for the info... my only question is to raven1.

 

when you said you had your barrel machined down to the 10.5" so you can keep the factory hop-up at stock factory configuration what do you mean exactly? if i were to get a tight bore that ran the full length of the outer barrel would that effect my hop-up in a bad way vs good? i apologize if i sound like block head.

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when you said you had your barrel machined down to the 10.5" so you can keep the factory hop-up at stock factory configuration what do you mean exactly? if i were to get a tight bore that ran the full length of the outer barrel would that effect my hop-up in a bad way vs good?

 

What I Mean Exactly,

 

My Outer Barrel is essentially the Stock Factory KJW M4 Barrel.

Only the very End of the barrel was cut down on a lathe for a total length of 10.5" or 266.7mm.

I did this so the hop up assembly is in stock factory form - Only the length was changed.

Stock KJW Inner Barrel was still recessed into the 10.5" barrel.

The Cradle Airsoft Tight Bore Inner Barrel was machined to match my outer barrel perfectly!

 

A Full Length Tight Bore Inner Barrel Will NOT Negatively Affect Your Hop Up At All.

( Well As Long As You're Using A Cradle Inner Barrel )

The Hop Up Assembly Doesn't Care How Long Your Barrel Is.

It Only Cares That It Is Assembled Correctly!

 

Please Remember:

 

Use teflon tape to keep the inner barrel securely in place in the outer barrel.

Teflon tape the muzzle end of the inner barrel,

Teflon tape just in front of the Hop Up Assembly,

Use a little extra wrapping around the barrel as the Teflon tape will compress - Being teflon it will slide inside the outer barrel smooothly.

This Mod produces consistent shot groupings as the barrel is NOT "Bouncing" around inside the outer barrel.

 

The process is as follows:

 

Remove outer barrel from gun,

Remove inner barrel / hop up assembly from gun,

Remove flash hider,

Remove metal fore end / cover from gun,

Measure out 10.5" from where Barrel Nut Contacts the Barrel - NOT From The Very End of the Barrel - But Where the Barrel Nut Fastens the barrel down.

Machine on lathe,

The outside of the barrel at the muzzle end is the correct diameter @ 1/2" or 12.7mm

Machine threads on Outside Diameter of Barrel which is 1/2" - 28 TPI

Since a lathe is being used you can go clock wise or counter clockwise with the threading - Your Choice

 

Using the section of the barrel that was cut off as a template

lay side by side with metal outer front section,

Mark the metal outer barrel front section,

Cut front section ( I used a band saw ) so that the muzzle brake threads are exposed.

All Done,,

 

 

Edited by Raven1

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@suicidalsnowman

NO - In Stock Factory Form the Magpul A.S.A.P Plate Will NOT fit on the KJW/ M4.

 

To answer your question - Having the Ability to use a single point attachment stock plate is 1 of 3 Reasons WHY the mod is being performed.

 

MILSPEC Buffer Mod Will Facilitate:

 

1. Allow for use of 'Legacy' latch plates - Specifically - Latch Plates that allow for AMBI Single Point Sling Attachment.

 

Here are a few examples,

http://www.brownells...SLING_CONNECTOR

http://dynamicarmame...pter-detail.htm

https://www.danielde...l&product_id=78

 

2. Allow for Proper fitment of MILSPEC stocks - Looking for 100% Zero Movement

 

3. Allow for greater after market choices in Buffers, Buffer Springs and Buffer Tubes.

Buffer tubes choices will grow to 4 - 5 - 6 position option(s).

 

This is important to me because I Not Only use my KJW M4 for Airsofting but my KJW M4 also pulls double duty as a training rifle to save money on brass. The Economy of motion and More Importantly the Manual Of Arms MUST Be Identical so that the exact same habits are maintained. The intent is to avoid "Training Scars" and to be consistent.

Edited by Raven1

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@Raven1

 

Well thanks for saving me from finding that one out the hard way!

 

I doubt I'm going to be able to find anyone in the UK with the requisite taps so for the moment I'll have to put up with it being out of spec.

 

Although to anyone with a Magpul CTR stock, does the friction lock cut out the stock wobble?

Edited by suicidalsnowman

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anyone putting in the TB notice that the hopup seems fatter around the new barrel?

 

That's because the channel where the hop bucking fits into is not deep enough. If you have a caliper, you can measure between the stock KJW inner barrel and your TB.

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I have a question for anyone out there that has both non-serialized and serialized guns (Phenom1, thats you most likely):

 

Have you observed any difference in hardness of the bucking between the two models. Kai and I were on the phone yesterday discussing the hop issues some people are having and it seems like most if not all that are having problems own a non-serialized gun. Im thinking that the rubber compound could have changed between runs and resulted in a stiffer bucking on non-serialized guns. I know people are adding material to the hop arm but the more I study this issue I think the hop arms are all identical and the fix that people are doing is just curing the symptoms of the problem and not the actual problem itself.

 

@suicidalsnowman:

 

The lock on my CTR cuts out about 95% of the wobble. If you crank on it the stock will wobble but during normal use its negligible and a non-issue for me.

Edited by t_hum

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I have a question for anyone out there that has both non-serialized and serialized guns (Phenom1, thats you most likely):

 

Have you observed any difference in hardness of the bucking between the two models. Kai and I were on the phone yesterday discussing the hop issues some people are having and it seems like most if not all that are having problems own a non-serialized gun. Im thinking that the rubber compound could have changed between runs and resulted in a stiffer bucking on non-serialized guns. I know people are adding material to the hop arm but the more I study this issue I think the hop arms are all identical and the fix that people are doing is just curing the symptoms of the problem and not the actual problem itself.

 

@suicidalsnowman:

 

The lock on my CTR cuts out about 95% of the wobble. If you crank on it the stock will wobble but during normal use its negligible and a non-issue for me.

 

Travis,

 

I have not opened up the barrels yet. I'm waiting for the inner barrels you sent me. Once I get them, I will take everything apart and take notes and pics. I have extra hopups that I ordered from Clare. I will compare all of them.

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Doesn't this gun take VSR rubbers? It needs its unique one then?

 

Edit:

Nowadays my english is not in its finest days. Hopup bucking = hopup rubber, right?

Edited by emp3ror86

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@Phenom1

 

I can't wait to see what you come up with on this. I am going to try and take my gun out this weekend and try it with reavier BB's but i was not impressed with the hop up on my gun when I took it out a few weeks ago.

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Doesn't this gun take VSR rubbers? It needs its unique one then?

 

Edit:

Nowadays my english is not in its finest days. Hopup bucking = hopup rubber, right?

 

Some have speculated that this gun takes VSR-10 rubbers. I looked at pictures online and, to me, it doesnt look like its quite right. The insides may be indentical (I dont know) but the outside is all wrong and lacks the ears necessary to lock into the hop-up unit halves.

 

Yes, bucking and rubber are the same.

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That's because the channel where the hop bucking fits into is not deep enough. If you have a caliper, you can measure between the stock KJW inner barrel and your TB.

the TB im talking about is the madbull one i got from THUM.

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Some questions I could use help with... Assuming there's answers.

 

1) On full auto, the first 3-4 rounds fly straight. Anything after that, the bb's start cutting downward sharply, as if the hop-up is upside down. Semi-auto is fine.

 

2) Is there a guide to removing the hop-up chamber? (Before I do it myself.. just in case I ruin something.)

 

3) Is there a guide or listing for combinations of rings and FPS for T_Hum's velocity reducer?

 

 

4) Is there are way to fit full stocks, or stocks like the Magpul PRS stock to the KJW?

 

5) Are any ambidextrous selectors around? I don't think so, but I thought I'd ask.

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Some questions I could use help with... Assuming there's answers.

 

1) On full auto, the first 3-4 rounds fly straight. Anything after that, the bb's start cutting downward sharply, as if the hop-up is upside down. Semi-auto is fine.

 

2) Is there a guide to removing the hop-up chamber? (Before I do it myself.. just in case I ruin something.)

 

3) Is there a guide or listing for combinations of rings and FPS for T_Hum's velocity reducer?

 

 

4) Is there are way to fit full stocks, or stocks like the Magpul PRS stock to the KJW?

 

5) Are any ambidextrous selectors around? I don't think so, but I thought I'd ask.

 

1) Make sure you dont have the hop set too high. Having it really high can cause weird issues. Also, any chance you are getting left over silicone lube in the hop chamber from your cleaning/lubing?

 

2) Yes,

 

3) I posted it a while back but its so temperature and gas dependent it was meant just to serve as a guide. In any case here they are again:

Tests done with .20g bbs, propane, hop off, 70 deg F, and using the o-ring in front of the listed spacings...

 

0.000 | 385

0.040 | 360

0.060 | 340

0.080 | 325

0.100 | 310

0.120 | 285

 

4) No full stock options yet as far as I know. I haven't worked on one nor have I grabbed a RS stock to see if it could be made to fit. Im sure it could be with a custom part or two made.

Edited by t_hum

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the TB im talking about is the madbull one i got from THUM.

 

I would surmise then that there are a few more differences between serialised and non-serialised guns, including hop bucking.

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Not that Ive observed. I've personally installed barrels in both non-serialized KJWs and Japan spec TK's in the last month using the standard cut barrels I send out to everyone. They all fit without a hiccup. I suppose its possible that there are some weird out of spec rubbers out there but that seems unlikely at best.

 

@prodigy:

 

Are you having a problem or just saying it seems fatter? Im not following if you were making an observation or having some issue.

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Some have speculated that this gun takes VSR-10 rubbers. I looked at pictures online and, to me, it doesnt look like its quite right. The insides may be indentical (I dont know) but the outside is all wrong and lacks the ears necessary to lock into the hop-up unit halves.

 

Yes, bucking and rubber are the same.

 

I see, thank you. I hope such high-quality third party manufacturers like Prometheus will notice this outstanding product and start selling buckings for it. I had fancy dreams about using firefly buckings once I finally claim mine and enter the gbbr world. :)

 

Is your custom tb barrel going to be listed at your webshop?

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