I would like to make a suggestion to anyone new to FAL's (FALFILES). That said a metric gas regulator is different then an inch. It goes 1-7 an inch goes 1-11, if you have a metric FAL remove the Front sight post entirely and take cleaning tool or guitar string or a drill bit and clean out the gas port. If you look into the hole where your front sight post was you will see the gas port, make sure it is free of crud and dirt once agian this only works for metrics. Once you are positive it is free of crap put the front sight post back in, either with a tool or a filed down pair of needle nose pliers. By doing this now you will know you are operating with full gas allotment. The inch is diagonal drilled hole that you can get to from the gas regulator, clean this out just the same. The lower the number the gas you are giving to the piston, I try to get mine set as high as possible so I have room to crank it down if I need more gas.
As far as shooting until it locks back I have never bothered with this because all mine have locked back if you are having this trouble I would check your recoil spring. I shoot one at a time whatch how far my shells are ejecting, and regulate the gas until I have it putting them out maybe three feet from me. I have had only problems with failure to eject if you are having this problem give it more gas, in other words close that little hole under the gas regulator up more.
I drill my gas ports out just a smige on all my FALS and that way I am assured full gas blow back. An 18" barrel you can open up .116" to .118", a 16" barrel .118"to .120" I would not recommend going any larger then that, any larger could shave off to much brass and cause fauling.