Originally Posted by surebet
Will the 203 shell have it's own "base", use another shell for propulsion, or be... caseless?
The 203 round will be optimally used with a custom 40mm driver cartridge. It will telescope inside the hollow skirt at the back of the projectile for a total package length around 5". You can also muzzle load the projectile with a bb blasting Moscart type driver, but you'll have to load two items with each shot and you'll lose some barrel length.
I wish I could have integrated the launch capability in the projectile, but I'm trying to keep the launch weight down for safety reasons. Also, an integral driver and shell would increase the total complexity of the system (simpler to have separate modules) so you'll have to dump the driver charge into a dump pouch, but it'll be a stubby cartridge that would look similar to a real grenade hull which is kind of neat.