The Variety *I saw* propelled differently than Cased ammo. Whereas Cased has an explosion that's guided down a barrel propelling the bullet, without the barrel and such the case and the bullet fly apart ala shrapnel style. This variety of Caseless had a controlled burn that didn't consume all the fuel within the length of the barrel, but only shortly thereafter. It seemed to be a hybrid between Caseless and Gyrojet where the propellant travelled with the bullet, but on the outside of the round, or so it was explained.
That SOUNDS like an incendiary or tracer round, actually, not caseless ammo. Both have attached burning material that might look like a rocket exhaust.
The only reason that Gyrojet works is that it HAS a case. For propellant to work effectively it needs confined space. Gyrojets have the confined space contained inside the bullet, with a tiny nozzle in the rear for the burning propellant to shoot out of, pushing the gyrojet round in the other direction.
In regular ammo, cased and caseless, almost all of the "push" is from the expanding gasses inside the confined space of the barrel. Once the bullet leaves the barrel, the gasses don't have a lot to push against anymore. Even if you had burning propellant attached to the bullet, it's not going to impart any significant "push" to the bullet after it leaves the barrel - all the energy just scatters into the air.
I wasn't aware of the changes to propellant and the like. SR doesn't seem to be using that variety, unfortunately.
Yeah, there's a lot of tech stuff that Shadowrun didn't keep up with.
I know the US Army has purchased a whole slew of caseless ammo weapons (http://www.vincelewis.net/metalstorm.html), but they are configured a bit different than normal. The barrel exists purely to hold all the rounds, and reloading consist of changing the barrel out. They got around all the weak-spots by sealing the barrel/magazine. The guys I know that fired them say the recoil is less than the normal mounted weapons (M-240, Mk-19, M-2) that have a lot lower rate of fire 300-1200 rpm vs. 1 Million rpm.
Yeah, the Metalstorm appears in Shadowrun as the "Sakura Fubuki" (cherry blossom storm) firearm.
In real life, it looks like the Metal Storm makers are concentrating on vehicular or mounted scale weapons now - apparently there is no military interest in small arms personal scale versions. I can imagine why - carrying a bunch of tubes of ammo, and having to muzzle or breech load them, is inconvenient compared to regular old magazines.
-k