I was refering to the thing on the top, which on modern day weapons jettison the emty bullet casings.(cant remember the english word for it) But you're right of course... It doesnt have to be what it looks like.
Edit: Might be for energy cells as well, but IMHO this seems a little unpractical...
It looks like an M-1911 Colt .45, but without a hammer. It could have a self-contained alternate means for igniting the propulsive agent in the projectile. The word Dyret is looking for is ejection port, and since the weapon has one, I'm leaning for classifying it as a ballistic firearm, slug-thrower, or whatever you wish to call it
I agree that it wouldn't make sense to have a magazine full of seperate energy capsules that discharge and eject, as opposed to a single-piece magazine. All it needs to do is regulate and release the amount of energy needed to be considered lethal, until the magazine is spent, rather than have a few extra unnecessary steps to do the same job.