TexasCHLforum.com

If no actual discharge of a firearm is needed for training, extreme adherence to the three (or four depending on your source) rules of safe gun handling is absolutely called for. Someone has already mentioned the use of blue guns, SIRT pistols and the like, and simunitions have been mentioned already as well. There is another alternative as well for a classroom setting where actual discharge of the firearm is not warranted -- a training barrel inserted instead of the regular barrel of a firearm. Brownell's sells them for three or four popular semi-auto platforms. The "barrel" is yellow plastic and fits in the gun in place of the regular barrel but does not allow for chambering of a round at all.
http://www.brownells.com/shooting-acces ... 26106.aspx