Short cycling FN-FAL

[General Disarray]

My brand new second-hand FN-FAL was CAI assembled G1/Imbel was advertised as having a short-cycling issue, but I snatched it up anyways knowing that someone here could likely help me get to the bottom of it.

I have it dialed down to 1 on the gas regulator before my PMC's will cycle. The rounds cycle but are only barely opening the bolt enough to eject/load. It doesn't *always* throw the bolt far enough back to hold it open on the last shot.

I measured the gas piston: .430". I tried to stick my calipers into the gas tube but I can't seem to get a read on it; I don't know how.

This might not be a factor, but it seems odd: the receiver cover doesn't fit flush against where the bolt meets the upper receiver. It has a gap on the left front edge about the thickness of a quarter. Is this letting gas escape, or does it not matter? I'm just trying to get to the bottom of where the gas is escaping before it flings the bolt back.

 

[tribbles]

Assuming that you don't have the gas plug turned to the grenade setting, two things come to mind:

1) There's something in the gas block obstructing the flow of gas. Make sure the gas port is clean and free of crud and gunk that the angry beavers at Century might have missed.

2) The barrel was screwed in such that the gas block is canted in relation to the receiver. This misalignment would cause the gas piston to bind in the tube.

As for the receiver cover, it doesn't matter.

 

[goon]

Yep, clean it first. You should be able to clean the gas port really well by taking the front sight post out. After you do that you should be able to look directly through the port and into the barrel.
Also, make sure there isn't any crud or rust in the gas tube.
If that doesn't work, maybe try just replacing the gas tube and plug. Too much wear could allow gas that should be working your action to escape.
If that doesn't work you may need to drill the port out. I've done this before with a peice of 1/4" thread stock wrapped in tape, a vise padded with several thicknesses of cardboard and a cordless drill with the right sized wire guage drill bit. It's not as scary as you might think but it should be a last resort.

 

[chris in va]

Friend of mine had the same issue. No matter what he did with the gas adjustment, it still had a bad FTE issue. He blew through $200 worth of ammo doing it.

 

[General Disarray]

Friend of mine had the same issue. No matter what he did with the gas adjustment, it still had a bad FTE issue. He blew through $200 worth of ammo doing it.

Did he figure out how to fix it?

 

[Sunray]

"...CAI assembled..." It could have a mixture of inch and metric parts. Century is known for that with FAL's. And for assembling rifles out of parts bins with zero QC.
Have a look at the gas piston rod for straightness too. Plus the gas plug.
"...I don't know how..." There's a guage, but you'd have to find one and it wouldn't be cheap if you could. A set of inside calipres would do it. They're actually spring loaded guages that you put in a hole then measure with a micrometer.
It'd be less fuss to just change the gas cylinder and rod, but you need to know if your rifle is inch or metric. Gunparts has Brit L1A1 cylinders at $16.50 each. The rod is $27.90 each.