Dunno exactly WHEN he began. I AM reasonably certain he was the first to put one on a Glock 19 for actual carrying, which is what Hambo referenced.
Bonnie Harmon of the Army MTU actually "pioneered" the use of RDS on competition pistols, when he surprised everybody (except his team mates) by showing up at Camp Perry with one on his wad gun in 1968.
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