First trip to the range was a qualified success. FAL fired every time I pulled the trigger, didn't explode or fall apart, fed and ejected manually. That's the qualified part. No matter where I set the gas regulator, the action would not cycle. Checked to see that the piston would move in the gas tube. Checked to make sure the "A" was up. After I got home, checked to make sure the hole in the gas block wasn't blocked. Wish I had thought of that at the range. Any ideas on what could be causing the problem?