Front firing blank guns vent flame and smoke from the end of the barrel that is not plugged.
Front Firing Blank Gun Demo Video
The top firing blank guns are also called side venting blank guns. The top firing blank guns have a plugged barrel and a small red plastic insert inside the end of the barrel as an added safety precaution. (That red tip is only visible from the front view.) The top venting blank guns vent the flame and smoke from the shell ejector in the automatic top firing blank guns and from the revolving bullet chamber in the top firing revolver blank guns instead of from the end of the barrel.
A lot of people ask me if you can convert the blank guns in to Real Gun, to fire the live ammunition.
Blank guns are made from inferior metals and cannot handle the pressures from live ammo. The barrel is usually designed to be permanently blocked and not designed for projectiles.