[as for who I am, I heard the cry of shitty science and answered it. I come and go with the wind, going only where I am needed. I'll probably make an app soon]

ANTI MATTER BEAMS? FORTY KEKS GOY.I don't know what the fuck that is for one, I am imagining a squirt gun shooting antimatter at some other ship. Let's forget for a second that antimatter is a particle, not some sort of EM radiation that can be "beamed", I suppose the fucking clod means spraying antimatter at a ship. And while that would work, and be fucking effective, why not just USE antimatter to shoot things really fast at the enemy ship. Antimatter is a very powerful thing, and the mechanism for shooting at ships would probably be so fucking obtuse and large, not to mention who knows how slow the antimatter would go [antimatter is also much harder to produce than some bits of metal or plutonium to shoot at the enemies, so while being less efficient theoretically if all the antimatter connected, it would be more ergonomic]. Also, anti-hydrogen or some sort of anti-plasma would be gasses or maybe liquids. WHO KNOWS HOW GASSES BEHAVE IN A VACUUM? OH YEAH, THEY FUCKING SPREAD OUT DUE TO BROWNIAN MOTION. 

Also, lets imagine for a second you could get antimatter going fast enough to be viable in space combat, and then lets imagine it goes in a beam, all that you will get is a big fucking explosion, not some sort of neat cut.

And another thing: "Oh wow, these people have big anti-ship weapons that are really good. My only recourse is something that will REMOVE PLANETS FROM EXISTENCE." Good logic there.

And another thing, fix your fucking cartridge sizes - every modern cartridge is way more than 2x longer than it is wide, and there are very good reasons for this. Maybe you should follow suit. Unless your guns are railguns, which I suspect they are, in which case you do not want your slugs to be very thick, seeing as ideally they would punch through armor and either explode or just mushroom out. Also, this would let you store loads more, and not have to use so much energy for the same anti-ship capabilities.