View Full Version : L1A1 Piston Binding Due to Gas Tube Pin

May 12, 2017, 00:09
So I got my charging handle issue sorted out, but now the piston was binding after assembling the gas system. I took the gas tube pin out, and it drops free.


So now what? :cry:

I have the pin, which is standard size. But we know it does not fit. So I use a smaller pin - where do I get one?!

I am sure this has come up, someone knows the answer!!

May 12, 2017, 00:22
You may of experienced interference due to either the flat section of the gas tube was not completely flat at say bottom dead center.
That or the tube may be screwed in too far.
I experienced a similar issue once as I was reassembling my Brit L1A1. I tightened the gas tube as far as I could with the flat section at bottom dead center and then tried the gas piston for fit before installing the pin. The piston was binding.
I backed the gas tube off one full turn and problem was solved. I believe the flat section is slightly tapered and may of been part of the cause.
Hope this helps.
BTW, I am not aware of an oversized gas tube pin, just interference issues from time to time.

May 12, 2017, 09:09
Gotcha. Great! :biggrin:

I will try this tonite.

May 12, 2017, 15:45
Yes, what he said. Tube will compress if over-tightened and bind on piston.

Sometimes putting the piston head in the front end of the tube off the gun and giving a very subtle pry to 6 and 9 will relax it.

I often turn the face back a thread to get a fresh mating surface, and then a hand reamer (like a case mouth reamer) to be a slight bevel on the leading edge.

FAL is not supposed to be tight. There is supposed to be wiggle. I have not gotten a reason for it. I have not read a UK standard. I have read comments from UK armorers of timing to tight, but this seems to be a local choice not supported by any documentation and in conflict with FN spec.

May 12, 2017, 22:18
Totally worked! You guys rock! :tongue: