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KJW M4

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I made a new upper. KJW TK SPR GBBR, thoughts?

(please ignore the 20 round magazine with live rounds, just wishing the rifle was real hehe)

IMG_20120830_143055.jpg

 

WOW!...Amaizing gun dude, .40's a must for this one!

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@ Shabby. the inner barrel is modified AEG Prometheus 6.03mm diameter/ 510mm lenght barrel. I am yet to test it hehehe, There are many things to consider to make this a performer sniper rifle... from the quality of inner barrel mod to increasing the power source to compensate the lenght of the barrel. It can be done by either using more powerful gas or stronger hammer spring. Hope this performs well, if all efforts are exhuasted and does not perform the way I want it, this project will be scratched. Let's see. =)

 

Longer barrel plus more power from hammer or gas :-O doesn't a longer barrel in a gas gun already increase power quite significantly (of course this depends on how much gas is released). At least this was what I experienced with Tanaka m700 series sniper rifles.

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Longer barrel plus more power from hammer or gas :-O doesn't a longer barrel in a gas gun already increase power quite significantly (of course this depends on how much gas is released). At least this was what I experienced with Tanaka m700 series sniper rifles.

 

Right, depends on how much gas is released. I heard from someone locally that the gas released by stock KJW M4 GBBr is just enough for the stock short barrel that came with it. So I am yet to test for myself with longer barrel tomorrow, lets see. But i can only have a concrete result when I borrow my friends chrono... maybe over the weekend. I'll keep you guys posted.

 

I had the same experience with my gas m700 before ;) (see my avatar)

Edited by Cj Radge

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A friend and I have been playing around with barrel lengths and diameters for a stock KJW and other gbbs and we have observed the following:

  • because we're dealing with compressed gas, tightening the barrel diameter from 6.03 to 6.01 or tighter exponentially increases the gun's power with diminishing returns.
  • Extending the length of the barrel also increases the gun's muzzle power, up to a certain point. After that point, the gas fully expands in the space of the barrel and no longer causes the bb to accelerate.
  • Simply tightening the barrel increased output by about 50 fps.
  • Extending the barrel increased output by about 50 fps. Once past 365mm in length, muzzle velocity began to drop once again.

What we want to test further:

  • increasing the hammer spring tension will not raise FPS for shorter or tighter barrels but it may increase the muzzle output for longer barrels that are past the threshold of returns in the above observations.
  • modifying the v2 bolt o-rings to increase/decrease fps may also affect thresholds.
  • Temperature also affects this performance, but to what extent?
  • Would it be better to have a surplus of gas volume expanding in your barrel or not?

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Glad my tutorial helped you =) Nice work on the teflon ring. Even here in my area, that washer is hard to find, I just found mine lying around the house. For those who cannot find a washer, they can just sand down the inner buffer tube, 1mm is good enough ;).

 

Hell, I made my washer out of duck tape and did the same for a friend.

Edited by freon

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Would it be better to have a surplus of gas volume expanding in your barrel or not?

 

You want to use the expanding air as much as possible, i have read countless times in gas sniper threads how excess air causes inaccuracy. What happens is the bb exists the barrel with turbulent air around it, tumbling it out of its path.

 

In fact, there are ways to prevent this. I have seen these mock suppressors that have a bunch of little chambers inside, like the real thing, in order to channel the turbulent air away from the bb right after they both exist the barrel. :)

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@ Shabby. the inner barrel is modified AEG Prometheus 6.03mm diameter/ 510mm lenght barrel. I am yet to test it hehehe, There are many things to consider to make this a performer sniper rifle... from the quality of inner barrel mod to increasing the power source to compensate the lenght of the barrel. It can be done by either using more powerful gas or stronger hammer spring. Hope this performs well, if all efforts are exhuasted and does not perform the way I want it, this project will be scratched. Let's see. =)

 

CJ, I don't think you need to screw with the hammer just yet. Remember how you fiddled with the bolt o-rings to increase/decrease fps? Set the o-ring to increase the gun's fps. You'll have more gas pushed into the barrel. From there, just figure out what FPS you want your gun to be shooting at.

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You want to use the expanding air as much as possible, i have read countless times in gas sniper threads how excess air causes inaccuracy. What happens is the bb exists the barrel with turbulent air around it, tumbling it out of its path.

 

In fact, there are ways to prevent this. I have seen these mock suppressors that have a bunch of little chambers inside, like the real thing, in order to channel the turbulent air away from the bb right after they both exist the barrel. :)

 

Landa, my thoughts exactly! With some foam and cut-outs from a soda can, I think one can make some pretty decent baffles that should increase accuracy.

 

Sorry for the multiple posts. Been a while since I've checked these boards.

Edited by freon

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What I did to my kjw M4 barrel was use Teflon tape and wrapped it maybe 1 time around the inner barrel that touches the outer barrel enough for no wobble. I noticed that instead of my shots being either left to right sometimes, there were all straight but with drop due to hop.

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Right, depends on how much gas is released. I heard from someone locally that the gas released by stock KJW M4 GBBr is just enough for the stock short barrel that came with it. So I am yet to test for myself with longer barrel tomorrow, lets see. But i can only have a concrete result when I borrow my friends chrono... maybe over the weekend. I'll keep you guys posted.

 

I had the same experience with my gas m700 before ;) (see my avatar)

 

Nice :) Good luck on your upgrades. Hope it all goes well, I'd totally build a marksman rifle out of a KJ m4 if the results were worth it!

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What I did to my kjw M4 barrel was use Teflon tape and wrapped it maybe 1 time around the inner barrel that touches the outer barrel enough for no wobble. I noticed that instead of my shots being either left to right sometimes, there were all straight but with drop due to hop.

 

That's a good and simple mod to do. I did it to mine too for pinpoint accuracy. There are two hop mods on this thread as stated, the simplest one is to wrap your hop-arm in heat-shrink tubing (I used duct tape) and adjust according to the bb weight you use.

 

I use .32 black bbs and shoot at 350 fps using .2 bbs. The heavier weight bbs give me a bit more range and accuracy. As a result, I'm able to tag people at a distance that makes them say "Where'd that come from?"

 

Operators using KJW M4 Gbbr and insertion using Nimbus 2012 Bling Edition

(Left: Freon and me on the right) lol

 

 

CJ, you had to show it didn't you?

 

Nice :) Good luck on your upgrades. Hope it all goes well, I'd totally build a marksman rifle out of a KJ m4 if the results were worth it!

 

My KJ, as seen above, may look like a MK18 mod 1, but it performs like a marksman's rifle. I've gotten it ridiculously accurate and shooting black bbs makes it hard for people to 1. dodge my shots and 2. see where I'm shooting from by tracing. You can get your KJs ridiculously accurate so after that, it'd just be a matter of getting the form to follow the function.

 

lastly, KJW has released a newer version of their hop up assembly. It's more responsive to adjustment and doesn't need any mods. I'm seeing good results from mine.

Edited by freon

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I need to get that too!

 

Nothing that im doing is working with the current hop up design... no heat shrink allows me to almost backspin 0.28's perfectly in the highest setting, but if i add ONE layer, it overhops in the lowest one :fear2:

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I would e-mail KJW to find this information out.

 

As for the parts, they looked similar to the original hopup and I didn't notice any changes outright. Only that the dial snapped into place more crisply as you turned it and it was more responsive.

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Does anyone know if this stock would fit on the KJW M4 without wobble? http://shop.ehobbyasia.com/accessories/stocks/aeg/magpul-pts-ctr-stock-for-marui-m4-m16-black.html

 

Also, what length rail system would fit the CQBR?

 

I use the same stock, but would recommend the one without the clamp, with some electrical tape it will fix the wobble not the clamp part of it. For the rail system I believe its a standard carbine length (7in?)

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