Mr. Rawles:
These sage comments on FN FAL gas adjustment from my friend and colleague, John Krupa, Director of Training for DSA [an American maker of FN FAL clone rifles. The following is re-posted with the permission of DSA]:
“Not knowing that one can control gas-flow on this weapon has led to countless customer-service calls to DSA, complaining that the rifle ‘doesn’t work.’ The following is laid out in great detail in the Owners’s Manual, of course, but we are happy to explain to each owner how the gas-regulator works and then walk them through correct gas-regulator adjustment. Invariably, when we’re finished, like a miracle, the rifle suddenly runs fine!
(1) The gas vent is directly behind the base of the front sight. We start the process with the gas-regulator set to the full-open position, which is # 7 on the gas-regulator dial. The vent-hole will be visibly open all the way. Next, we start to close off the gas-regulator vent by turning the dial clockwise two clicks, which will place it at # 6. You will now see that the vent hole is partially occluded. From here, we can start our live-fire, function testing.
(2) Charge a magazine with a single round of ammunition. Insert the magazine into the rifle and chamber the round. Holding the rifle in a normal, standing position (bench-resting is not recommended) aim into the impact area and fire one round. When the bolt fails to lock back, [we can conclude that] not enough gas is driving the piston into the bolt group for a complete cycle of operation. So, close the gas regulator another, single click, which will put it at 5 1/2, and then repeat the one-shot drill. Continue to close off the gas-regulator, a click at a time, until consistent (three in a row) bolt-lock is achieved
(3) When the bolt thus consistently locks to the rear after firing a single round, insert a magazine charged with five rounds, load the rifle, and fire all five in rapid succession. Once again, the bolt needs to unfailingly lock to the rear as the last round is fired.
(4) Once your rifle passes the ‘five-round test,’ close the gas-regulator two more clicks! The gas regulator is now ‘set.’ Just about all rifles we issue for student use have a final set at 4 to 4 . That is pretty standard.
(5) When the rifle gets hot, dry, and dirty, and starts short-cycling, you
can use the gas-regulator dial to quickly make incremental increases in gas
pressure, instantly restoring the rifle to normal functioning.
I don’t recommend closing the gas-regulator completely, as you suggested in your last Quip, unless absolutely necessary. What concerns me is not excessive wear-and-tear on the rifle. The DSA/FAL is a robust, military rifle that is designed for heavy use in hostile environments. It will take whatever you can give it! Nor is my concern with accuracy. Practical accuracy is unaffected by gas-regulator adjustments. Nor is my concern with recoil attenuation. Soft recoil is nice, but we can all handle recoil. The real problem is with case-extraction that is so violent it may result in cases being literally pulled apart as the bolt moves to the rear. The front half of the case may thus be left in the chamber, resulting in a stoppage that cannot be corrected
in the short term.
With regard to ammunition:
Ammunition quality is all over the map! Ammunition from dubious sources, reloads for example, typically exhibit inconsistent head-space and inconsistent pressure. DSA, of course, recommends against the use of such poor-quality ammunition, except in exigent circumstances.”
Comment: John Krupa is the resident expert, and I will surely defer to his judgment on this issue, and my advice to FAL owners is that they adhere to his,
foregoing instructions. The thorny issue is, of course, “exigent circumstances!” When I have my FAL, some magazines, and a supply of ammunition about which I know little,
and I’ve been invited to participate in a fight that is starting immediately, best bet is to begin with a rifle whose gas-regulator is closed off. I’ll put up with recoil, and I’ll take my chances with case-separation, just as long as I can be assured my rifle will complete each cycle of operation. Conversely, when I know what ammunition I’m going to feed it, and I have time to go through the foregoing gas-regulator adjustment routine, and a range where I can do the mandatory live-fire, I will surely tune my weapon to maximum advantage. No contestation there.
Of all dubious ammunition, the most suspect is reloads. Cases that have been reloaded multiple times are stretched, weakened, and thin in spots. They are the ones most prone to case-separation, described above, and inspection may not be helpful. From the outside, one can seldom tell if a case wall is dangerously thin. “Once-fired-reloads” is a commonly-used platitude, but how can anyone really know how many times a particular case has been reloaded? Reloads are thus not recommended for use in any autoloading rifle. – John