The CO2 12 gram should just fall out. I've never seen one get stuck.
fps = feet per second. When you play at a field they usually make you chronograph your marker (test how fast it is shooting). Most fields require an upper maximum of 250-280 fps. In theory any marker shooting a paintball with a muzzel velocity of 280fps will shoot as far as any other marker with the same muzzel velocity. It doesn't matter if the ball is exiting a 6 inch barrel or a 16 inch barrel, if it is going 280 fps it should travel a set distance. Spin changes things.