AUTHORS NOTE: I think the railgun was too ambitious. And ultimately this game is going to be decided by the navy. We can leave the ground combat stuff until later. However, I'm writing this with the intent that we might be able to salvage something we can use later. Until we know what we're dealing with, we should perhaps rein in some ambitions.
Also, if this can't be done in a revision, Madman, we can drop it into the pool of designs for the next design phase.
Proposal:
Instead of attempting to immediately skip up a few steps in ballistic arms development, let's step back and recreate the tried and true. Our pistol arms are enough to kill a man, even if rather ineffectively. The various weaknesses resulting from the fact they are only about as strong as the plastics they are constructed, and the difficulty of 3D printing the weapons. They are perfect for interstellar peacekeeping, since there isn't going to be the fear of someone putting a 100 holes in the hull all that easily. They are terrible at war when a hundred rounds downrange may save one's life.
While we have references to fully automatic variants of these classes of weapons, it is agreed that, that might be a step too far too quickly for our people in R&D. Thus, the designs presented would increase the caliber and length of the weapon, but it would keep it as a semi-automatic. Like our pistols, a detachable magazine could take in ammunition, as well as fit various sights to adjust for various conditions in operational zones.
Each weapon would be a combination of metal and composites to produce a sturdy yet lightweight weapon.