We used to use them at work until we got the new UTM rounds approved. What it is, is a 9mm pistol round with a paint projectile made by Simunitions. Actually, the "paint" is a thickened liquid detergent that washes out better than the new UTM rounds from your clothes. The entire upper is swapped out and the actual barrel is quite a bit shorter than the overal barrel length. Think of a counter-bore job from hell! LOL I would say the actual barrel ends near the front sight assembly. Anyways, the plastic magazines hold 20 rounds but are a PITA to load. There is a hole near the back side of the magazine's top where you can use an M9 cleaning rod to depress the follower to assist in loading. The bolt is also different and that is swapped out with the entire upper. Really, I didn't care for them as much. Accuracy isn't as good as the UTM rounds, there are far more failures to feed and they have more of a tendency to jam one stuck projectile on top of another until the barrel is completely plugged. We still use the 9mm rounds in converted M9 pistols for active shooter training and they work well there but in the M4 conversions, not so much.
