Planning on a design which is something like the Mass Effect M-8 Avenger Assault Rifle. The final design will depend on accomodation of components within the shell.
Currently waiting on CNC build.
Going to try out some Rctimer 5010-620KV Multicopter Brushless Motors for the flywheels. Since they're outrunners, the outer shell spins, which should hopefully work well as a flywheel by itself.
An Arduino will be used to drive the brushless motor controllers and ancillary functions.
Hooked up the motors today and fired a test shot. It made a nice thud on impact. :-)