The US Navy Gunsights used during WWII and the early post wars years was limited to just three main types of Gunsights (and their many late war and early post war adaptations and evolutions); all of them being adaptations of British sights:
- The Mark 8 illuminated sight used for fixed gunnery that was a modified version of the British Barr & Stroud GM2 fixed gun sight (designated the Fixed gun Reflector Sight Mk II);
- The Mark 9 illuminated sight used for flexible gunnery that was a modified version of the British Barr & Stroud GJ3 free gun sight (designated the Standard Turret and Free Gun Sight Mk III);
- The Mark 18 lead-computing gyro Gun Sight for use in aircraft turrets that was adapted from the British GGS Mk IIC (turret) lead-computing Gunsight.
If the number of gunsights used was limited, the Navy designations used to name their sights and associated equipment’s was rather confusing and complicated. The following designations were used: Illuminated Sight, Gun Sight, Gun Sight System, Sight Unit, Aircraft Sight system and Aircraft Fire Control Sight system. You could therefore for example find the Gun Sight Mk 18 Mod 6 System which used a Sight Unit Mk 10 Mod 0 (basically a Gun Sight Mk 18 fitted with a Range Unit Mk 18 Mod 0) or the Sight Unit Mk 8 Mod 0 that is part of the Aircraft Fire Control system (AFCS) Mk 6 Mod 0 that should not be confused with either the Mk 8 illuminated sight or the Sight Unit Mk 6. Confusing isn’t it !!
I’ll do my best to clarify all this in the following pages relating to:
- Reflector Sights: mostly the Mk 8 Illuminated Sight and its adaptations that are the Mk 20 Illuminated sight and the Mk 1 Sight Unit.
- Computing Sights: Mostly the Mk 18 Gun Sight and its many adaptations that are the Mk 10, Mk 21 and Mk 23 Gun Sights and the Mk 8 Sight Unit.
- Sight Heads: Mostly for the Mk 8 Illuminated sight