While at Sig Academy I found an unfired 9mm Simunition round. Mike on my squad who makes barrels warned me that it was too large to fit in normal 9mm chamber. That way a real 9mm round couldn't be use in a sim gun/barrel, because it would fall to far into the chamber.
Ah yeah of little faith. He was right about most 9mm chambers, but I have a 929 revolver, whose chambers are just a tad bigger than standard 9mm. So I put the sim round (UTM brand knock off, not actual Simunition brand) in a moon clip and fired it off.
First off the "primer" would not fire double action, but undeterred, I shot it single action and it did fire. No where near as loud as an old-timey cap gun. I shot it at a piece of paper-over-wood at 3' and it tore the paper and embedded the marking material just at the surface.
HERE'S THE WARNING.
Being that UTM Simunition uses an aluminium case it expanded just enough to be a pain to get out. There wasn't enough force to drive the primer back flush so I had to tap my cylinder out of the frame first. Then I warmed up the cylinder with a heat gun and drove the case out with a punch. No damage. I was planning on a full scrub and polishing the chambers anyway this week, so no worries. Just be forewarned not good to fire this in revolvers.