The primary thing I noticed in the links jinx posted was projectile travel speed.
Those machine guns and lasers had almost instant travel time from the firing ship to the target, even over longer ranges. High travel speed means the shot cannot be dodged easily.
Right now, even at very close ranges, it's a pain in the ass trying to hit a dodging fighter in a capship because they can get out of a shot's way before it reaches them. At long distances, you'd be lucky to hit another battleship without it dodging your fire.
6000-10000 m/s travel speed severely reduces the enemy's ability to dodge your fire, and for 'flak' or 'point defense' cannons it would be the best route to go - weapons that have extremely high travel speed, but lower refire rate and damage. They'd be very difficult or even impossible for fighters/bombers to dodge, but would be ineffective against larger ships.