A rough schematic diagram to the workings of saurai flak cannons
Like most saurai weapon systems, the basic flak cannons employed en-masse by the fleets of the various legions are in many ways an apostasy of simplicity: combining traditional explosive propulsion with rocket propulsion and Gaussian (coilgun) propulsion. The benefits of guided munitions with their high initial dV and a trend towards relatively high rates of fire apparantly make them ideally suited to the ultra-short range scenarios that are ubiquitous in a contested orbit scenario.
Most saurai flak cannons have a maximum effective engagement range of 0.25-0.5ls and are notable for their lack of a minimum effective engagement range. Their ammunition is produced shipboard in the case of larger ships. In smaller ships they are stocked up via the use of ammunition teleporters. This stock of ammo spreads more evenly spreads out the energy usage of flak weapon systems across the engagement and allows them to operate at a punishing rate of fire should something stray within effective weapon range. When no targets are within effective engagement range, flak cannons are often fired at a highly reduced rate of fire over the course of a battle.