They would also manage to really wad things into the gas cylinder of the C1/C2, often a brush wrapped with cleaning material. I recall some being soaked with gasoline and burned to attempt to loosen. This in addition to all the tricks to fire blanks full auto. Sometimes in post Ex inspections these home built full auto mods were found still in place. Piece of cork behind the firing pin caused it to protrude from the breech causing runaway firepower. Fortunately this was discovered before firing with ball ammo!.