When I was in tech school in the AF the instructors said they used blanks to kill snakes (less the blank adapter of course.). Without the blank adapter all the gas goes out the muzzle. Not enough or none goes into the gas tube which cycles the action. This is why the rifle did not feed another round.
Thank you for your service!
Second blank round the 1SG fired did move the BCG enough to cock the hammer, eject the spent brass and chamber the next round.
Attributed that to the upright muzzle and pressure from the cup on the muzzle.
