Weapons Technology

The weapon technology of the Expanse is advanced, but not excessively so. Primary shipboard weapons are large railguns and fusion powered torpedoes carrying a small variety of warheads. Torpedo warheads are either nuclear, conventional high explosive or plasma, which are small fusion reactors designed to explosively overload. The Point Defense Cannons (or PDCs) are conventional bullet firing multi-barreled Gatling-style automatic cannons. While the TV show has PDCs firing almost constantly, they would more logically use short, high rate of fire bursts aimed at incoming missiles. They can be used at close range to engage other ships, but would mainly be useful against unarmored civilian ships or lightly armored smaller warships.
Lasers are mentioned, but never seen except as targeting or communications. Lasers might be superior PDC weapons depending on their range and power requirements.
Small arms are broken down into two general categories: conventional projectile guns intended for use in most normal gravity situations and recoilless/low recoil weapons for zero gravity and EVA combat. The conventional weapons are advanced projectile guns, but no lasers have been seen, nor do there appear to be any personal railguns. They may be caseless or liquid propellant firearms. The low recoil weapons launch rocket propelled projectiles such as those used by the old Gyrojet weapons.