With reference to the artwork.
Though the gun bears some resemblance to a bullpup Lasgun (TM), it looks like a Traveller style Gauss Gun (magnetically accelerated and spin stabilised kinetic energy weapons) or a gyrojet.
My reasoning is as follows:
Magazine placement - the bullpup location adjacent to the telescopic stock means not much room for the recoil of the receiver. Gauss weapons' receivers do not recoil (Newton's Third Law still applies to the weapon) and gyrojets "recoil" forward (you cock them by moving the receiver forward, pulling the trigger releases the receiver which pushes the round back on to the firing pin. The round moves forward pushing the receiver back into firing position, and popping the next round into position. I cannot remember why the exhaust of the firing round does not cook off the next round or the whole mag).
The shape of the magazine is odd, but that might be down to receiver design.
Laser weapons are not dependent on magazine to "receiver" placement, and there is a lot of fun forward of the pistol grip so is there a balance advantage with a bullpup arrangement?
Same with non round based plasma/fusion weapons.
Maybe I should go and do some painting....
^__^