FN FAL Gas system

[Charlie]

What is the right way to adjust the gas system on a FN FAL?

[MAX7.62]

If you have a bolt hold open - load 1 round, set the gas adjustment on 7, fire the round. If the bolt does not lock onto the hold open, reset the gas adjustment to 6 and repeat. Continue until the bolt locks onto the hold open. Most rifles will function properly set on 4 or 5.
If your rifle is not equiped with a bolt hold open, then you will have to load 4 or 5 rounds in the mag and go through the above until the rifle cycles the next round properly. If you have a jam during this operation, remove the jam and inspect the cartridge for damage. Dont' take any chances with a damaged round, bullets is cheap, rifles is spensive!
Ultimately you want to set the gas adjustment to the most "open" setting where the rifle will cycle properly. You will find that new factory .308 will cycle the action if the gas adjustment is set more open, say 6 or 7, but with surplus ammo the settings are again, usually functional around 4 or 5.

[MAX7.62]

NOTE: If you have a Century L1A1 made around 99 to 2000, check the gas piston to see if it is a 1 piece or 2 piece gas piston. Century tried to save some bucks at one time by using a cheap to produce 2 piece gas piston. These 2 piece gas pistons were, in my opinion dangerous because they could seperate. I have seen rifles out of the box that wouldn't function because the 2 piece piston was not straight and true. Look on the piston rod just behind the piston head for wrench tooth marks - like it was assembled with a small pipe wrench (don't laugh, I think they really did this!) If you see this, then you probably have a 2 piece piston.
TAPCO, DS Arms, or Brownells are some good choices to find a good 1 piece piston. I generally prefer DS Arms for new internal parts for FAL's. DSA is top notch and I don't scrimp on internal/functional parts (or ANY parts for that matter) that can hamper the reliability of a weapon.

[BluesJunkie]

Originally Posted by MAX7.62

NOTE: If you have a Century L1A1 made around 99 to 2000, check the gas piston to see if it is a 1 piece or 2 piece gas piston. Century tried to save some bucks at one time by using a cheap to produce 2 piece gas piston. These 2 piece gas pistons were, in my opinion dangerous because they could seperate. I have seen rifles out of the box that wouldn't function because the 2 piece piston was not straight and true. Look on the piston rod just behind the piston head for wrench tooth marks - like it was assembled with a small pipe wrench (don't laugh, I think they really did this!) If you see this, then you probably have a 2 piece piston.
TAPCO, DS Arms, or Brownells are some good choices to find a good 1 piece piston. I generally prefer DS Arms for new internal parts for FAL's. DSA is top notch and I don't scrimp on internal/functional parts (or ANY parts for that matter) that can hamper the reliability of a weapon.

I Check My Century FNFAL; The Gas Piston Is 2 Piece With The Wrench Tooth
Marks Like You Stated. Fortunately, I Had On Hand A Spare Gas Piston That
I Purchased From DSA Three Weeks Ago. The 2 Piecer Is Now In My Scarp
Metal Collection[I Recently Brought Metal Lathe Now I Got Some Practice
Metal To Learn The Lathe!]. Many Thanks For Posting This Warning!