In 'No Second Place Winner' by Bill Jordan, when he wasn't advocating planting alibi guns, he had an extensive section on Wax Bullets, which he used for the majority of his training. Details were provided on how to make them and how to practice best with them.
Bill could hit an asprin tablet from 5 paces, quick drawing from the hip, with a wax bullet.
He even had a special electric target for practicing indoors with his wax bullets. As I recall, a timer would activate a 'clown nose' red light in the siloutes head, indicating the time to draw and fire.
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I've often though that Wax Bullets would be ideal for training using the ultralight pistols like the 340, as the lack of recoil would allow a otherwise impossible level of practice (few would be willing to bang out 200+ a day .38's out of an 11oz revolver.)