KSC MP7 GBB Won't Fire Properly

[Stealthee]

Hello everyone, my KSC MP7 GBB (Taiwan) won't fire properly. I have a RA-Tech NPAS, RA-Tech Hardkick set, and Bomber Steel Bolt Carrier installed, which was done a few weeks ago. The gun was shooting fine up until yesturday:

The BB would load properly when you pull the charging handle, when you pull the trigger, you can hear the gas being released from the magazine, but no BBs exit the gun's barrel.
Right after the first shot, it would load the next BB like normal, but because the first shot didn't exit the gun, it's still in the barrel now with the 2nd BB that was loaded. Each time you pull the trigger, more BBs pile in the barrel.
Another note: when I try it in Full-auto, the first shot sounds normal, but then it hisses as if there's no gas left, but when I take the magazine out and lightly press the flow valve, it's really hard which means there's still gas in it.

Can anyone help me with this? I took the gun down and see if there's anything loose or that needed to be lubed, but everything seems okay.

[Thenooblord]

something with the rocket valve, the NPAS may be all the way out putting all the gas to blowback and none to the barrel, that would make no BBs firing but the gun still cycles

[HeadlessChicken]

Since they were my mags, let me try out a few shots to see if we can narrow down the issue between either your gun or my mags. BTW, did you try all the mags with the same problem or just 1 or 2?

EDIT: No problems on my end...curious though, my first couple shots were sub 100FPS then suddenly 368FPS.

[Stealthee]

Originally Posted by HeadlessChicken

Since they were my mags, let me try out a few shots to see if we can narrow down the issue between either your gun or my mags. BTW, did you try all the mags with the same problem or just 1 or 2?

It's doing it to my one and only magazine too. I've been trying to figure out the problem for the last few hours.

@Nooblord, I had the NPAS installed and it shot fine for a while. It shot a few rounds yesturday and today, but now it's not firing at all. And with the NPAS, I set it to the lowest (mostly closed) and the highest (mostly opened), it didn't make a difference.

EDIT: @Headless, I tried mines, and I think just 1 of yours.

UPDATE: I just switched back to stock parts, same result. BB doesn't exit gun. Gas sounds like it works. Could it be a magazine problem?

[kullwarrior]

SOLUTION:
http://www.gasguns.info/forum/viewtopic.php?f=42&t=3902

This is common problem for NPAS

[Stealthee]

Originally Posted by kullwarrior

SOLUTION:
http://www.gasguns.info/forum/viewtopic.php?f=42&t=3902

This is common problem for NPAS

What if it still does it in the stock valve?

Edit: So it still didn't fire regardless of upgraded/stock parts. I put back the Bomber Steel Bolt Carrier, NPAS and Hardkick. I tried dry firing it and I can feel a bit of air coming out of the barrel. Is the pressure weaker than before? I don't remember, maybe a little. But it still doesn't shoot a BB out.

[cjboi]

its your hop up my friend!!! it probably swelled up and the BB's get stuck in the barrel. You did say, you put the stock valve and and everything right? then the problem has to be the bucking or the spring that pushes the whole nozzle.

[cjboi]

you might wanna check the hop up bucking.... always put lube after using your gun 3-4 times.... this guy will help you dismantle the whole thing, and just try to see whats happening within the barrel.
YouTube- MP7a1 field strip 1.mp4

[cjboi]

and ya check your piston cup... check if its still in whole piece, since the force(impact) of the heavy steel bolt carrier is alot heavier than the normal aluminum bolt carrier. It could break the piston cup and the cylinder in the bolt carrier. hope all of this can help.

[Stealthee]

The problem has been identified and 99% solved. The problem was that the hop up rubber/bucking was enlarged or changed in a way that the hole got tighter so the BBs couldn't pass through; gas couldn't past through it, but you can still push it through with a stick or something, which took some force to push through.

After some fiddling and forceful installation, the hop up tore. I put back what's left of the hop up back and reassembled the gun to see if it still works. It does. Semi & full-auto both work. I have ordered a replacement hop up, but this will do for the time being.

Thank you all for your input.

Here's a piece of the hop up that was torn off (by accident):

[juicy]

Don't soak your rubber in silicone oil? I hope you aren't doing this as of yet...

Edit: that being said, I'm glad to see that you've figured out wtf was wrong. Yay!

[Danke]

Who has the hop up rubbers in stock?

[HeadlessChicken]

Probably have to order direct from KSC, I have no idea if any retailers sell the hopup for the KSC/KWA MP7.

[Stealthee]

Tokyo Model Company is the only retailer so far that I have found that carries it. I just ordered one today.

And no Juicy, I haven't intentionally applied any oil to that part of the gun. I was excessively lubing the other parts of the gun that may have trickled down there. Anyways, I'll try to keep it dry from now on.

[cjboi]

I already ordered my parts just in case something happens to my gun. Lol