As one that has intimate knowledge with the FAL I understand. Years ago it was noted that with a correct gas setting switching from Port/Aussie/Hurt to SA required closing the gas setting 1-1/2. The Crono said that they were close but the results......
Have seen many builds that had issues with pulling the rim on brass to excess. Timing issues that can be corrected. My last build needed .050 trimmed from the gas piston to stop the pulling of the rim.It all happens in Milliseconds. [Flower] And I am staying out of the .223/5.56 debate. ;)