Chattanooga, 5"/50 caliber deck gun, probably port side forward.
Type	Naval gun Coastal gun
Place of origin	United States
Service history
In service	1904
Used by	United States Navy
Wars	World War I World War II
Production history
Designer	Bureau of Ordnance
Designed	1900
Manufacturer	U.S. Naval Gun Factory
No. built	Mark 5: 87 (Nos. 200–286) Mark 6: 64 (Nos. 293–356)
Variants	Mark 5 Mods 0–3, Mark 6 Mods 0–2
Specifications
Mass	Mark 5: 10,294 lb (4,669 kg) (with breech) Mark 6: 10,550 lb (4,790 kg) (with breech)
Length	Marks 5 and 6: 255.65 in (6,494 mm)
Barrel length	Marks 5 and 6: 250 in (6,400 mm) bore (50 calibers)
Shell	Mark 5: 60 lb (27 kg) armor-piercing Mark 6: 50 lb (23 kg) armor-piercing
Caliber	5 in (127 mm)
Elevation	Mark 9: −10° to +15° Mark 12: −10° to +25°
Traverse	−150° to +150°
Rate of fire	6–8 rounds per minute
Muzzle velocity	50lb:3,000 ft/s (910 m/s) 60lb:2,700 ft/s (820 m/s)
Maximum firing range	19,000 yd (17,000 m) at 25.3° elevation

The 5"/50 caliber gun (spoken "five-inch-fifty-caliber") was the first long barrel 5-inch (127 mm) gun of the United States Navy and was used in the secondary batteries of the early Delaware-class dreadnought battleships, various protected cruisers, and scout cruisers. They were also refitted in the secondary batteries of the armored cruiser New York and the New Orleans-class protected cruisers. They were later used on cargo ships, store ships and unclassified auxiliaries during World War II as well as in emergency coastal defense batteries.^[1]

The Mark 5, Nos. 200 – 286, was a 50 caliber naval gun of a simplified construction by combining the breech piece along with the chase hoop into one long tube that was shrunk on from the muzzle. Mod 1 was a Mod 0 gun that was relined with a conical nickel-steel liner and an additional gun-steel chase hoop that extended to the muzzle that was secured by a nickel-steel locking ring. Mod 2, gun No. 280, had a slightly different liner with Mod 3, gun No. 245, was a Mod 0 gun with its gun-steel tube replaced with a nickel-steel tube with a gun-steel chase hoop added that extended all the way to the muzzle. The Mod 3 gun had a longer chase hoop and shorter jacket compare to Mods 1 and 2.^[1][2]

The Mark 6, gun Nos. 293 – 356, was the bag-ammunition equivalent to the Mark 5 gun. Mod 0, Nos. 323 – 356, had a single jacket constructed of nickel-steel, that replaced the jacket, chase hoop and locking ring of the Mark 5. Mod 1, Nos. 293 – 306 and 308, was built of gun-steel with a chamber of a different design with some external differences to fit it onto different mountings. The Mod 2, Nos. 307 and 309 – 322, had the same chamber as the Mod 0 but was otherwise almost identical to the Mod 1.^[1][2]

The 5-inch/50 caliber gun was also used on cargo ships, store ships and unclassified auxiliaries during World War II.^[1]

• Bluejackets Manual, 1917, 4th revision: US Navy 14-inch Mark 1 gun