Firing in the aft arc. That reminds me of something.
I thought about this question for a while, and I actually think that the configuration we see in most sci-fi, with the guns on one end and the engines on the other, is actually more correct. You know why? It's because deceleration is death. It makes you an easier target. The last thing you want to be doing is braking when approaching a target. You want to be moving at a very high rate of speed, but have side thrusters for translational movement for stochastic motion to avoid incoming fire. Think of the YOLO engagements from Children of a Dead Earth, where you just go straight at the fuckers with your strongest armor facing them to soak up fire.
When you intercept the target and get within weapons range and start shooting, you want to fly past them, pull a 180, and then burn retrograde to enter the target's orbit while firing opposite your direction of travel. Another important thing to keep in mind is that projectile weapons share the velocity of the ship. If your ship is moving at 10 kilometers per second relative to the target, and you simply jettison a chunk of metal, that's pretty much going to hit them like it was fired out of a mass driver. You wouldn't even need a railgun. Just release projectiles while approaching, and fire lasers while on a departing trajectory.
Who needs guns? Your engines are already accelerating your ship and everything in it. Just dump kinetic rods out the side. Maybe have little thrusters on them so they can translate from side to side and form a shotgun-like spread pattern. Space projectiles should not be dumbfire. They should be something more akin to EKVs and have maneuvering thrusters of their own, so they can position themselves in just the right formation and then "go dark" when they enter enemy sensor range. The ideal design would be two-stage, with a thrust ring located over the center of mass, right in the middle of the low-observable, inert kinetic penetrator core. As soon as it closes with the target, the thrust ring itself would be jettisoned and release a huge burst of radar chaff to make the exact location of the penetrator harder to acquire so lasers can't shoot it down.
Have I mentioned that I'm evil and full of evil thoughts?
Anyway, this is for approaching "stationary" opponents already orbiting a planet. The rules are totally different in open space. If your enemy matches velocity with you, then you need some way to accelerate projectiles, of course.
