Blank ammunition rounds have various uses, such as providing a less lethal alternative to live rounds for firearm training, cinematic and theatrical productions, and starter pistols. Blanks tend to consist merely of an ammunition cartridge with a paper, wood or plastic wad instead of a bullet. You can produce simple blank rounds yourself with a few supplies.
Feed smokeless powder into the case. Fill the case to approximately where the base of the bullet would be if the round were live. Do not pack the powder excessively tight, however, as this may result in depriving it of oxygen, thus making it impossible to fire.
Cut a piece of cardboard (any kind of cardboard should do) with a pair of scissors at a dimension which would snugly fit in the case. This will be your wad, which will serve mostly to prevent the loss of the powder before the round is fired. The fit must be tight enough that it will not dislodge from simply moving the round.
Insert the cardboard wad into the cartridge. Do not insert it deep enough to excessively pack the powder. Nothing else need be inserted. And, in order to avoid the creation of potentially lethal projectiles, the insertion of anything else is discouraged.
Test fire your blank ammunition under controlled circumstances. Fire at a large mound of soil, barrier of sandbags or other such obstruction to ensure that any debris that might be in the barrel will be stopped before it can harm anyone. Make sure to bring another person with you, so rescue services can be called in case of emergency.
If your firearm is designed to fire black powder rounds, use black powder instead of smokeless powder. You can find pre-made blank rounds at many ammunition stores, or even online.
Do not attempt to remove bullets from live cartridges -- this is dangerous, as you could set the round off, resulting in severe bodily harm or death. Empty cases and smokeless powder can be purchased at most firearm accessory stores. Although blanks are less lethal than live ammunition, they can still cause injuries and death (especially at close range, or if there is debris in the barrel). Never point a firearm at any living thing you don't intend to kill, and treat every firearm as if it's loaded with live ammunition at all times.