The incredible amount of energy used by Maxim is far, far more than sufficient to ignite a powder charge. It's extreme overkill. You'd only need that much juice to power a railgun or coilgun. The thing uses as much energy as SIX Subachs. The gun also does not make the "bang" a propellant charge would.
The Maxim's firing characteristics, energy consumption, and description make NO sense aside from an electrodynamic mass driver.
Now this is pure speculation as far as delving into the unkowns of the fs universe anyone can't consider. We don't know what conventional explosives are in the fs universe (aside from bombs). And you're really not thinking about how energy intensive a gun would need to be to require an electronic system (Gattling gun/mini gun comes to mind). That much energy isn't just used for burning the powder to expel a bullet, but is also used to support the high rapid firing rates of big automatic guns. The maxim is a big high rate of fire gun (so why not consider this?).
However it does not have rail propelled ammunition, so it's not a railgun. The other thing is that it's quite clear that the maxim spits out bullets. Another thing to keep in mind is that in the scp the maxim gets replaced from using weapons energy to actually firing bullets that you need to reload. if it spits out bullets why does it need to even use the weapons energy of your fighter? One is for the drive system of the ammunition. Two is for the fact that V didn't do a very good job making a bullet spitting weapon. They made an awesome weapon, but they never put into the game a bullet counter so you know how much ammunition you have left, and instead tied the maxim down to your weapon energy exclusively (SCP fixed this).
The maxim does have a smoothbore barrel. So since it's not a railgun, then it's most likely a coilgun or a normal gun. And since the tech description doesn't much bother with mentioning something as big of a detail as explosive tipped bullets, but rather only mentions conventional explosives once...that doesn't leave much either in the area of explosive tipped bullets. If maxim bullets were explosive tipped, i'm pretty sure the tech description would say it outright since that's a pretty main characteristic of the gun as well as the fact that it uses bullets. The tech description for the maxim is horrible.
But you can deduce that it's not a railgun (no rails). So that leaves a coilgun (most likely). And the detailess conventional explosives being mentioned (this detail doesn't suggest much at all). So there you have it. It's a coilgun! And at least i'm looking for an explanation to why it is as opposed to you woolie wool going off and saying nothing more than "IT'S A RAILGUN/COILGUN! IT'S A RAILGUN/COILGUN! IT'S A RAILGUN/COILGUN! IT'S A RAILGUN/COILGUN!IT'S A RAILGUN/COILGUN! IT'S A RAILGUN/COILGUN!IT'S A RAILGUN/COILGUN! IT'S A RAILGUN/COILGUN!IT'S A RAILGUN/COILGUN! IT'S A RAILGUN/COILGUN!IT'S A RAILGUN/COILGUN! IT'S A RAILGUN/COILGUN!IT'S A RAILGUN/COILGUN! IT'S A RAILGUN/COILGUN!IT'S A RAILGUN/COILGUN! IT'S A RAILGUN/COILGUN!IT'S A RAILGUN/COILGUN! IT'S A RAILGUN/COILGUN!....S-99's just talking out of his ass again".
Proof? Or will you just talk out of your ass?
At least i was providing something dumb****.