8"/35 caliber Mark 3 & 4 / 8"/40 caliber Mark 5 Naval Gun
Crewmen standing atop USS Indiana forward port side 8-inch gun turret, circa the later 1890s.
Type	Naval gun
Place of origin	United States
Service history
In service	Mark 3: 1890 Mark 5: 1894
Used by	United States Navy
Wars	Spanish–American War World War I
Production history
Designer	Bureau of Ordnance
Designed	1889
Manufacturer	U.S. Naval Gun Factory
No. built	Mark 3: 19 (Nos. 9–21, 33–37, and 51) Mark 4: 56 (Nos. 22–32, 38–50, and 52–83) Mark 5: 24 (Nos. 84–107)
Variants	Marks 3–5
Specifications
Mass	Mark 3: 29,400 lb (13,300 kg) (without breech) Mark 5: 40,151 lb (18,212 kg) (without breech) Mark 5: 40,621 lb (18,425 kg) (with breech)
Length	Marks 3 & 4: 25 ft 4.5 in (7.73 m) Mark 5: 28 ft 7 in (8.71 m)
Barrel length	Marks 3 & 4: 24 ft 7 in (7.49 m) bore (35 calibers) Mark 5: 27 ft 10 in (8.48 m) bore (40 calibers)
Shell	260 lb (120 kg) armor-piercing
Caliber	8 in (203 mm)
Elevation	Marks 3 and 4: -5° to +20° Marks 5 and 6: −4° to +13° Marks 7, 8, and 9: −7° to +14°
Traverse	Bow and Stern Mountings: −150° to +150° New York Amidships Mountings: 140° Brooklyn Amidships Mountings: 140°
Rate of fire	1890s: 0.5 – 0.8 rounds per minute 1900s: 2 – 2.8 rounds per minute
Muzzle velocity	Marks 3 & 4: 2,100 ft/s (640 m/s) Mark 5: 2,500 ft/s (760 m/s)
Effective firing range	Marks 3 & 4: 16,000 yd (14,630 m) at 20.1° elevation

The 8"/35 caliber gun Mark 3 and Mark 4 (spoken "eight-inch-thirty-five--caliber") were used for the main batteries of the United States Navy's first armored cruisers and the secondary batteries for their first battleships, the Indiana-class. The 8"/40 caliber gun Mark 5 initially armed the Pennsylvania-class armored cruisers.^[1]

The Mark 3 Experimental was a 30 caliber gun that used trunnions and had 11 hoops with the outer hoop starting 4 in (100 mm) from the breech and running out to the muzzle. The Mark 3s consisted of gun Nos. 9 – 27, 33 – 37, and 51. The production Mark 3 Mod 0 had removable trunnions, 96–97 in (2,400–2,500 mm) from the breech, 35 caliber gun that had 11 hoops with the outer hoop starting 4 inches from the breech and running out to 43.5 in (1,100 mm) from the muzzle. This gun was removed from service prior to World War I. The Mark 3 Mod 1 was constructed of tube, jacket and eight hoops while Mod 2 was identical to Mod 1 but with different steps under the chase hoops. Mod 3 was, for one gun, lengthened to 40 calibers and was removed from service prior to the start of World War I. Mod 4 was, also for one gun only, different from other Mods in having a ring shrunk onto the breech end, tapering the breech, and with a small balancing hoop screwed onto the front chase hoop. Mod 5 had the trunnions removed and the outer jacket threaded to accept a sleeve. Mod 6, gun Nos. 52 and 82 – 83, were constructed of nickel-steel in a simplified three-piece construction.^[1][2]

The Mark 4s were Nos. 22 – 32, 38 – 50, and 52 – 83. The original Mark 4 Mod 0 guns were identical to Mark 3 Mod 1 guns with the trunnion hoop and elevating band removed and with the threads formerly under the trunnion hoop being continued to the rear of the gun. This allowed these guns to be screwed into the sleeve of a two-gun turret mount. Mark 4 Mod 1 was one Mark 4 gun, No. 27, shortened by 0.66 in (17 mm) in rear of the threads. Mods 2 through 9 were for minor differences primarily for testing different mounting techniques. Mod 10 was for one gun cut down to 23 calibers and used for experimental work with high-explosive shells. Mod 11 was a Mod 4 gun, No. 72, with an alloy steel liner, uniformed rifling and modified chamber.^[1][2]

The Mark 5, Nos. 84 – 107, was a new 40 caliber design intended for armored cruisers and battleship secondaries and constructed of tube, jacket, three hoops and one locking ring. This gun had a muzzle bell. Unfortunately, the Mark 5 proved to be unable to handle the transition from black powder to nitrocellulose propellants as the new propellant burned more slowly, which allowed pressure to build up to unsafe levels as the projectile traveled down the bore. This problem was illustrated when Colorado blew off the muzzle of one of her Mark 5 guns during gunnery practice off Yantai, Shandong, on 22 June 1907. All Mark 5 guns were subsequently removed from service by 1908, lengthened to 45 calibers by adding a new liner and rehooped to the muzzle, redesignated as Mod 1 and then placed into reserve. Two of these Mod 1 guns were given a slightly different breech mechanism and gas seat and then designated as Mod 2. Pennsylvania-class cruisers were subsequently rearmed with the stronger 8-in/45 caliber Mark 6 guns.^[1][2]

• 8-inch gun M1888 - Army gun of similar type and era

• Friedman, Norman (2011). Naval Weapons of World War One. Seaforth Publishing. p. 173. ISBN 978-1-84832-100-7.
• "United States of America 8"/35 (20.3 cm) Marks 3 and 4 8"/40 (20.3 cm) Mark 5". Navweaps. 29 July 2016. Retrieved 15 October 2016.

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