RML 16-inch 80-ton guns were large rifled muzzle-loading guns intended to give the largest British battleships parity with the large guns being mounted by Italian and French ships in the Mediterranean Sea in the 1870s.

The gun was constructed of a toughened mild steel inner "A" tube surrounded by multiple wrought-iron coils, breech-piece and a jacket. Rifling was of the "polygroove plain section" type, with 33 grooves increasing from 0 to 1 turn in 50 calibres (i.e. 1 turn in 800 in (2,000 cm)) at the muzzle.^[2]

After a long design and experimentation period beginning in 1873, HMS Inflexible with its four guns, became the only ship to mount them, in 1880. By that time such muzzle-loading guns were already obsolescent and were being superseded by a new generation of rifled breechloading guns.

Two more guns were mounted for coastal defence in the Admiralty Pier Turret at Dover.

This was a second-generation RML gun, equipped with polygroove rifling and firing only studless ammunition and using automatic gas-checks for rotation.

• 112½-pound ¼ charge brown prism powder cartridge

The only two remaining example are in the ruins of the Admiralty Pier Turret, Dover, Kent, UK.

• List of naval guns