M4 throwing a fit.

[SinfulPain]

My M4 is deciding to throw a temper tantrum now, because I upgraded my P90, and didn't buy her any new accessories. She won't lob the BB's more than 50 feet now, and even SHORTER, if I turn up the hop-up.

I've pulled the upper reciever off, and it seems to be putting out plenty of air through the air nozzle... I don't wan't to have to replace the piston, though. I know its not the hop-up bucking/nub, or the air nozzle, because all 3 of those are practically brand new (less than 6,000 rounds through em).

The only thing I've done recently is re-lubed the gearbox, and I made sure not to use too much or too little.

Any and all advice (besides buying a new gun) is welcome. I love my '07/'08 JG M4 to death!

~Brian

[Exarach]

You messed up your airseal. It happens, Check the hop up and GB alignment, and the piston/head/cylinder seals.
Also check that the spring on the hop up is still there pushing back.

If you want to bring it over I can look at it for you.

[SinfulPain]

You messed up your airseal. It happens, Check the hop up and GB alignment, and the piston/head/cylinder seals.
Also check that the spring on the hop up is still there pushing back.

If you want to bring it over I can look at it for you.

I had to remove the spring, because it was pushing too far back, preventing the magazine from feeding the BB's. I'll make another spring for it, then. This time, it'll be shorter. Pain in the ass that originally, the spring was just fine, then it was too long. Checked it when it was "too long", and it wasn't getting caught. Oh well, I'll just make new ones, and see how they work.

~Brian

[Crono0001]

Make sure the air nozzle is actually connected to the tappet plate

I made this mistake twice

[SinfulPain]

Make sure the air nozzle is actually connected to the tappet plate

I made this mistake twice

It's still connected. Air nozzle still pulls back fully, and doesn't flop around.

I'll eventually make that spring. Just been too lazy to do it.

~Brian

[airsoftguy]

Why don't you check your piston head cylinder head and see if you have compression.

[azsworst]

Why don't you check your piston head cylinder head and see if you have compression.

If your going to do that, check the compression with the airnozzle on the cylinder head. And get a new O-ring.

[SinfulPain]

Why don't you check your piston head cylinder head and see if you have compression.

If your going to do that, check the compression with the airnozzle on the cylinder head. And get a new O-ring.

O-ring probably needs replacing, as I've never replaced it, and it has god knows how many rounds have gone through it... To check the compression, you just pop off a few shots, with your finger in front of the air nozzle (barrel removed, oviously), right? If so, I've already done that, and it's got similar compression to my P90.

~Brian

[AxisOfOil]

That's one way... but not the best by far. You can only tell if you have a total loss of compression (like your piston head came off or something like that) that way.

Remove the cylinder, piston, cylinder head and airnozzle from the gun.

Put your finger over the airnozzle (in the forward position if you can manage it... since that's where it is when it fires), still attached to the cylinder head and cylinder, and then try to push the piston through the cylinder head.

If the piston just glides right through, you have a compression leak. If you try and try as you might and can't get it to budge more than an inch... you have either very good compression or very weak arms.

[SinfulPain]

That's one way... but not the best by far. You can only tell if you have a total loss of compression (like your piston head came off or something like that) that way.

Remove the cylinder, piston, cylinder head and airnozzle from the gun.

Put your finger over the airnozzle (in the forward position if you can manage it... since that's where it is when it fires), still attached to the cylinder head and cylinder, and then try to push the piston through the cylinder head.

If the piston just glides right through, you have a compression leak. If you try and try as you might and can't get it to budge more than an inch... you have either very good compression or very weak arms.

The piston has always glided through, yet never showed an issue til now.

First, though, I'll make a spring for the hop-up unit, and see if that stops the problem.

~Brian