KJW M9

[balaclava ben]

Hey,
About a week ago I fitted a 150% spring set into my KJW m9, both bolt and piston springs, and it was firing alright until today. I was reducing the hop up on it as it was over hopping by miles and i realised that the blue atatchment at the back of the slide, (that chambers the BB's and channels the gas from the mag) was slightly loose, I didn't think it was to much of a bother. I carried on firing and the gun was misfiring a little bit, then lots of gas coming out of the rear end of the slide upon firing and gas efficiency reduced significantly. It then ceased to fire a bb, I took the slide off and had a look, the blue nossel was able to pull out (muzzle direction) by about 3 centimetres and the two little springs that keep the blue nozzle back were protruding out, one uncoiled and useless, the other was fine and i popped it back in. Now the gun will not chamber a BB on its own, if i pull back the slide manually to chamber a BB it fires fine but it wont fire more than 1, that is manually chambered, at a time.
So my question are,
1) Does anyone know why this has happened and is it due to the spring set
2) Where do i get a replacemtn spring for the blue nozzle?
Thanks
BB

[b_hazard]

Re: KJW M9

cant help on question im afraid, but i do have kjw m9 with the blue blowback chamber, i wanted to replace this with a metal blowback chamber, so if anyone can answer the question above, do they know if you can acquire a metal blowback chamber and where to get it from? soz to hijack ya thread dude, but could be useful to you! thanks

[balaclava ben]

Re: KJW M9

haha yeh no problem mate, if anyone has any sugestion that may help at all please just say!
cheers
BB

[dope_on_a_rope]

Re: KJW M9

Bigger springs never improve gas efficiency or the ability of the gun to cycle backwards.

Just for a second think about what you're doing to it. You're giving the slide more resistance, so the gas has to work harder to cycle the gun. Not just with the return spring, but also with the hammer spring. Cocking the hammer becomes much more difficult for it.
The hammer spring, is still doing exactly the same job it did before, it opens the valve, that's all. A bigger spring wont open the valve for longer, because of the way it works. The valve knocker opens the valve, and is then locked in place, till the slide reaches a certain point in it's rearward travel when it's released. So putting a bigger spring in there, doesn't mean the valve opens more like you might think, but it means the valve is open for longer, and uses more gas, because it's taking so long for the slide to overcome the increased weight of the hammer spring.
The only time a hammer spring is advised, is if you're getting light striking issues, because you're using very strong gas and the original spring wont cut it. The symptoms of this would be the first few shots not cycling well, and then once some gas has been released the gun starts to cycle well again. Or the gun not working on green gas very well, but working very well on abbey ultra or 134a.

The recoil spring again is increasing resistance, and should only be installed if the gun was catching on something during it's cycle. Even then I would advise against it. If the gun was working fine at one point, and starts catching, don't put in a bigger spring and cause more gas inefficiency. Find out what it's catching on, and fix it. In many cases, with cheaper guns, it can catch on the hammer, because the hammer sear has worn and the spur is resting higher than it should when in a cocked position.

My advice, try it first without the "upgraded" springs in it. If it works fine, happy days. If you're still having trouble with it feeding, sort out the springs in the blow-back chamber. You might get lucky and find something useful down a hardware shop for pennies. Or you might have to order from an airsoft shop and pay £5 for it.


As for a metal blow-back chamber. They don't exist as far as I'm aware. I wouldn't recommend it as an upgrade even if they did. Metal is a temperature sensitive material, and can contract when faced with very cold gas. There is a guarder enhanced loading nozzle for many guns though. Better materials if you needed a new blow-back chamber. But with GBBs especially, I tend to go with the motto, "if it isn't broken, why repair it?"

[balaclava ben]

Re: KJW M9

thankyou very much for your time and thoughts dope on a rope, very much appreciated. I'll try it with the original springs and see how it goes
Thanks again
BB