This picture features a brand new FN F2000 Bull-Pup modular "future" assault rifle, equipped with an under barrel mounted FN303 less-than-lethal launcher. This launcher can also be mounted on the M16-Style rifles (you are displaying yet on your website a photograph of an M16-A2 equipped with XM303/FN303/M303 under barrel laucher).
The difference between XM303, FN303 and M303 is: XM303: First prototype of this less-than-lethal launcher. The launching unit can be detached from its stock and attached under the barrel of every STANAG-type assault rifle.
FN303: Definitive version of the less-than-lethal launcher. It is an "independent" weapon: the firing unit can't more be detached from the stock for application on another rifle. M303: Firing unit of the less-than-lethal launcher, specifically made to be mounted under the barrel of a STANAG assault rifle.
Picture and information courtesy of: PIERANGELO TENDAS