KJW M4

[JT SANBORN]

I had the same problem before where the magazine don't released enough gas to push the bolt back and after a couple shots the gun stopped cycle. It was my hammer spring that was messed up and the valve knocker wasn't working properly cause of dirts. After I replaced the hammer spring, cleaned and greased the valve knocker. The gun back working to normal.

 

Oh in another note; make sure your magazine is not too loose in the magwell. That might cause your problem though. Push the magazine up into the magwell, hold it with your hand and fire a couple shots on semi to see what happen.

Good luck...

[jonjon]

Thank you guys for the quick replies! Gonna have a look at the gun as soon as possible and will post an update

[Hut73]

Just finished up my 2nd upper(long rifle), and thought I'd snap a shot of it w/ its real steel big brother. I SO can't wait to get this thing out on the field and get some quality time in with it, instead of time spent in the garage! Hope you like it!

 

[weekenny]

Looks great, where did you get the trades on the lower?

[ewashbrook]

Looks nice mate

[Hut73]

Looks great, where did you get the trades on the lower?

 

Thanks guys...

 

Landa mentioned some decals that he found at Tokyo-Model a while back. I had some other stuff to order, so I picked one up. It's actually pretty slick. We'll see how long it lasts.

[Landa]

i got the colt ones, Hut has some other ones, there is like 3 or 4 you can choose from.. :3

 

its crazy how durable they are, its like a metallic film with very strong adhesive on the back..

 

 

 

Here is my latest reincarnation, just waiting for my barrel nut to get here so i can install my 12 inch DD RISII, the XTM hand stop and my troy BUS kit

 

edit: i also installed a falcon 363mm inner and paired it with falcon's bucking... ill let you know how it does!

Edited October 23, 2012 by Landa

[weekenny]

Cheers guys. They still do them.

[delarosa]

Anybody tried filling down the mag external yet? Or bought the Stanag mag?

And I recently bought DD RAS, but theres no wrench, anyone know what should I use to replace the wrench to tighten the nut?

Edited October 24, 2012 by delarosa

[hwagan]

Anybody tried filling down the mag external yet? Or bought the Stanag mag?

And I recently bought DD RAS, but theres no wrench, anyone know what should I use to replace the wrench to tighten the nut?

 

If you've got a standard AR-15 armourer's wrench, the bit for tightening the stock tube castle nut will fit as well!

[delarosa]

If you've got a standard AR-15 armourer's wrench, the bit for tightening the stock tube castle nut will fit as well!

 

Sadly got no such thing, is there any regular tool that will fit though?

[hwagan]

Sadly got no such thing, is there any regular tool that will fit though?

 

If you're not too concerned about scratching the finish of the barrel nut, it can be done with a pair of needle-nosed pliers; It takes a bit of elbow grease and effort, but it can be done - You basically need to screw it on as tight as you can by hand, then get each point of the pliers in one of the tool notches, grip it nice and tight and tighten it up as much as you can. You'll get some marks on the notches, but it can be done - The barrel nut is hidden when the rail is installed anyway so it's not too much of a problem if you scratch the nut up a bit.

[weekenny]

Anybody tried filling down the mag external yet? Or bought the Stanag mag?

And I recently bought DD RAS, but theres no wrench, anyone know what should I use to replace the wrench to tighten the nut?

 

Disassemble the mag you'll see that the ribs are the only thing providing rigidity at the joins, take them away and I don't think the mag would take much abuse.

 

Not tried the Stanag.

 

You can use mole grips or stilsons to do it up, you'll easily get it nice and tight but will mark the nut. Pick up a G&P stock tube wrench, it's cheap and works a treat, won't damage the nut either.

[Hut73]

If you're not too concerned about scratching the finish of the barrel nut, it can be done with a pair of needle-nosed pliers; It takes a bit of elbow grease and effort, but it can be done - You basically need to screw it on as tight as you can by hand, then get each point of the pliers in one of the tool notches, grip it nice and tight and tighten it up as much as you can. You'll get some marks on the notches, but it can be done - The barrel nut is hidden when the rail is installed anyway so it's not too much of a problem if you scratch the nut up a bit.

 

And a black Sharpie does a great job covering up those scratch marks, if you're really worried about it...

Edited October 24, 2012 by Hut73

[ewashbrook]

And a black Sharpie does a great job covering up those scratch marks, if you're really worried about it...

 

Agreed, or some black enamel paint.

[delarosa]

Ah, thanks a bunch guys for the info, will try to get it done soon, I'll post a pic once my set up is all done.

 

Btw, does the AEG aluminium barrel feel heavy? I want to minimize weight on the front part to prevent another back pin breaking. The DD RAS I got is slightly heavier than my KA RAS, so I thought lighter outer barrel could do the job. Do you need to mod an AEG barrel heavily though? I read last time that its quite easy to instal an AEG barrel but Im not too sure about it.

[weekenny]

I modded a G&P barrel, it's very simple there are pictures in this thread. You basically have to cut the notch for the nozzle. I used a drill and a small file to do mine.

[ewashbrook]

Ah, thanks a bunch guys for the info, will try to get it done soon, I'll post a pic once my set up is all done.

 

Btw, does the AEG aluminium barrel feel heavy? I want to minimize weight on the front part to prevent another back pin breaking. The DD RAS I got is slightly heavier than my KA RAS, so I thought lighter outer barrel could do the job. Do you need to mod an AEG barrel heavily though? I read last time that its quite easy to instal an AEG barrel but Im not too sure about it.

 

Trust me, you'll hardly feel the weight difference

[Landa]

Eventful weekend KJW M4-wise....

 

a long post, as a lot of stuff happened, its worth the read as [spoiler alert] surprise surprise! guess whoe's V2 had a catastrophic failure? yea, and i was bragging that i hadn't seen a single failure documented online of V2's... me and my big mouth.

 

Part 1: First things first: finally the DD RISII is on it

 

its ACM and it came with a weird nut that according to a "tech" buddy of mine its "Classic Army threaded." Anyways, i bought a G&P madbull DD nut and fit fine (good fyi: imperial nuts fit on metric bodies).

 

The build is just missing the Troy BUS set, should be delivered next week, maybe a nicer torch later on

 

 

and yes, i bought a castle nut specifically for the DD nut (the armors wrench KJW ships with their M4's doesn't have one, as it has the faux outer buffer) for the guys above, this is how it looks, works perfectly:

 

 

Part 2: Now on to the failure:

 

 

 

The nozzle slams forward (to produce blow back) and is held (from going to far forward) by that little black plastic tab in the first picture. Apparently the force is so hard that it blew the whole front of the carrier... the zinc alloy/pot metal in this BCG is worse than plastic... look at that!

 

The BCG has (had) ~7k rounds, mostly used in very hot 90+ Fahrenheit conditions. This particular day was cool, mid 80s. I was just shooting semi, taking seconds between shots. No other damage was done.

 

The nozzle stayed forward preventing the chamber from closing. I thought the nozzle return spring broke, like always in this V2's, so i removed the mag and moved it around to confirm... it sprung back, i got excited and then the whole front of my carrier fell from the magwell. I got sad

 

Should i contact KJW? I have another carrier for now, but i like using two BCG's with different valve FPS ratings.. now im forced to choose one maybe KJW can give me a discount? i mean, save for the TBB and aftermarket bucking, its stock... i was even using the stock valve. (the other BCG had the cradle reducer)

 

I could try and contact them to let them know of the issue, maybe they release a V3. I can include how easily the BCG wears down in the area where the bolt catch engages and how nozzle return springs break constantly...

 

Nonetheless, it failed under normal operation! lol, if they tell me sanding the paint out reduces structural integrity eheh Come on T hum! Get those V1+ in stock! The V2's KJW is selling clearly have an inferior BCG design!

 

Part 3: Testing the 363mm falcon tbb and bucking

 

 

 

 

- Fitment:

 

Same wobble as the stock 10 inch KJ, as you can see in the 1st pic, my stock inner has some electrical tape shims. I did the same on the falcon when installing it, eliminated any wobble. The bucking is much tighter and harder than the stock, and it fits even better.. as you can see in the last picture. I heard the bucking "wouldnt fit" the hop up unit. Not true at all, on my V2 at least.

 

- Issues:

 

Bucking: the mound on top is too thick, even with no hop, 0.28's slightly over hop... with 1 click of hop (using the V2's 10 position wheel) it climbs several feet at mid 100's. Insane over hop, thankfully in my gun the "no hop setting" seem to give it the perfect amount of contact (as you will see in my testing). You might want to shave it a bit down, i know i will later on, get more flexibility, or do the TDC.. as that mod with this bucking should work very well.

 

TBB: No issues, you cant go wrong with that. Its a 6.03mm tube, it does what its supposed to. The finish is really nice, and it looks above average quality.

 

- Performance:

 

Accuracy: This is using a chair for support, and not trying too hard (i would have made an effort if i knew i was going to post it here later lol). It was saturday, so a bit windy due to Sandy, but not too much, a few mph. Temp: 83 degrees, using an all stock V2.. apart from the falcon TBB and bucking. Checked the distances using google earth. I only excluded 2 shots as outliers* (at 130 and 145.)

 

*NOTE: not "flyers" if i included them to my spreads, they would only add a few inches. I had zero fliers using this bucking, maybe due to it being such a hard rubber (60 degree) and the heavy BB's.

 

2nd NOTE: the bucking had less than or about 200 rounds shot through it, maybe not even fully broken in. The barrel had been cleaned when installed (again 200 rounds gone through, though clean BB's).

 

Distance : Spread

50 feet : 5 inch

100 feet : 11 inch

130 feet : 16 inch

145 feet : 18 inch

 

This is as far as my backyard goes, but I played on sunday with it, (where the bucking should have broken in already) and i could see the BB's path being incredibly accurate, i doubt the spread is more than 3 feet or so at 200 feet. Thats very good, man sized no problems at 200 ft I believe my BB's where getting into the mid 200s with not problems too, still being effective. I couldn't see them drop, they where too far out, but definitely more than 300, but way past their effective range. Well, the gun is shooting 540 fps.. at the the very least it should do this good lol.

 

Here is the paper target with all the shots, if you want, circles are 50, x's 100, circle plus x 140 and scratched out 145: http://imageshack.us/a/img94/3148/img1111oa.jpg (ignore the writing)

 

- FPS: Big jump! not very surprised considering its much tighter and almost 50% longer. Note, my KJ has a "magic pin" might increase my FPS a slight bit...

 

STOCK: 418fps with 0.28's (494fps with 0.20's) and with the falcon 363mm TBB plus bucking: 452fps with 0.28's (about 542fps with 0.20's).

 

NOTE: that "stock" reading was in the middle of the summer, very close to tipple digit temperatures. The chrono reading for the falcon TBB and bucking was done today, almost november and mid 80s. 15 degree difference is QUITE a lot in propane's PSI. So you should see a bigger change.

 

- for 60$ is it worth it? i think so.

 

Part 4: miscellaneous:

 

- Cradle velocity reducer: I had an issue with it where the FPS was really low. I contacted T hum, and he told me readings are never quite as high as the stock valve. Well, i took the nozzle apart for the first time, and now i know why they where so low. So if anyone gets this issue in the future, you know why.

 

I bought the reducer pre installed by t hum into the BCG. I guess whoever installed it didn't push the o ring all the way forward in the reducer, or it moved around. Point is the holes in the reducer cut into this o ring, making a sort of stopper, and prevented it from sliding all the way forward, replicating to what having all spacers in there be like.

 

here is a picture. I moved it around so you can see the cuts better.

 

 

- Broken nozzle return springs:

 

If you run KJW V2's like me, you probably have gotten this problem more than once. Well with this little mod, you can double to tipple the life of each spring. The springs like to (and only seem to) break at the ends. So, simply get some pliers and untie the last coil. Then shape it into a hook, kinda like hwo it was originally. if its tooo long, just cut it with the pliers.. you get the following:

 

 

 

on this picture i wasn't finished.. you want to close the hook like this:

 

 

Sorry for the long post, but i think it was good info.. just keepin' the thread alive fellow KJW users!

 

/landa out.

Edited October 29, 2012 by Landa

[weekenny]

Good V2 info.

 

The V2 bolt assembly is cheap from KJW sub $40 if I remeber right.

 

The TDC does indeed work well with the falcon rubber. Note: for those running the rubber and barrel in the UK 330 fps (cqb limit) is only just possible to achieve on propane with cradle valve.

[AG1212]

Good V2 info.

 

The V2 bolt assembly is cheap from KJW sub $40 if I remeber right.

 

The TDC does indeed work well with the falcon rubber. Note: for those running the rubber and barrel in the UK 330 fps (cqb limit) is only just possible to achieve on propane with cradle valve.

 

I actually wanted to ask about FPS. Which reducer would give me the lowest FPS, RA-Tech or Cradle? The problem is that I plan on using this gun as a DMR platform, seeing as I have a spare 20-inch barrel laying around. Now obviously this would give a big jump in FPS, and I need it to run below 1j :/

[weekenny]

Only an inner will increase FPS you could keep the stock inner in the 20" outer.

 

The RA tech ones bend and snap I'd only use the Cradle one.

[t_hum]

The Cradle Reducer will go sub 1J no problem.

 

A BCG Update:

The carriers are done being machined. I finished them up on Saturday so they go to anodize this week. Originally I didnt want to ship anything until all the new fancy packaging was in place but if we cant get everything 100% by mid November with the finer points of the packaging Ill probably start accepting orders anyways.

 

Sorry for the delay in any case. Please try to remember that Cradle is owned by an engineering/industrial design firm that we have to keep running on the day to day to keep my and my partner's families afloat. Sometimes our main line of work takes priority by necessity. It is our full intention to have Cradle standing entirely on its own here very shortly so these projects move much more quickly.

[frogfish]

Thanks for the update T_Hum! can't wait for the bolts!

[AG1212]

Only an inner will increase FPS you could keep the stock inner in the 20" outer.

 

The RA tech ones bend and snap I'd only use the Cradle one.

 

Well I know that I just don't see the point in having my gun 10 inches longer than it needs to be. So is it possible to have a 509mm-barreled KJW M4 running green below 1j? Temperature wise, Summer gets 25 degrees at most if we're lucky.

Edited October 29, 2012 by AG1212