Around 1870 the largest gun made by UK firms was the 320 mm RML (rifled, muzzle-loading) gun, with a mass of 38 long tons (38.6 t), firing an 818-pound (371 kg) projectile capable of piercing 16.3 inches (410 mm) of mild steel at 2,000 yards (1,800 m). This weapon was adequate for the needs of the time, but the progress of gun technology was very rapid. French industries soon made a 420 mm, 76 tonne gun.