We use dummy guns for ALL of our weapons retention and force on force training. No exceptions at all. You can not accidentally shoot someone with a solid piece of plastic.
We did recently have someone negligently shoot their self in the leg while reholstering during qualifications. It turned out to be a matter of leaving the finger on the trigger and trying to stuff the pistol back into the holster. Bang. Luckily not a crippling wound. It did blast some goo onto the gravel.
"A Liberal is someone who doesn't care what you do, as long as it's mandatory". - Charles Krauthammer