Firing Squads. There has to be something said for a method that takes into account the psychological effects on unintended parties. Traditionally in a firing squad, one gun was loaded with a blank round. This bullet is known as the “conscience round” and promotes diffusion of responsibility among the executioners. A heavy conscience is supposed to take solace in the fact that he may have had no part in a murder. A wax dummy round is sometimes used because has more recoil than a blank, making it harder to tell which rifle had no part in the execution. As reported by the BBC, in the execution of Ronnie Lee Gardner a wax dummy round was employed:

None of the firing squad will ever know for sure if he fired a lethal shot. One gun was loaded with a dummy – probably wax – bullet, which is said to deliver the same recoil as a live round.

From the BBC.

Department of the Army 1947 Pamphlet Procedure for Military Executions:

The officer charged with the execution will command the escort and make the necessary arrangements for the conduct of the execution. [The execution squad will consist of 8 men]. He will — (g) Cause eight rifles to be loaded in his presence. Not more than three nor less than one will be loaded with blank ammunition. He will place the rifles at random in the rack provided for that purpose.

Note: The above image is a blank, not a wax dummy round.