United States of America
6"/50 (15.2 cm) Mark 6 and Mark 8
Updated 03 November 2011

Originally used on pre-dreadnoughts and armored cruisers built in the late 1800s.  Also used on some auxiliary vessels during World War I.  When many of these ships were scrapped after the war and as a result of the Washington Naval Limitation Treaty, the guns were then used as coastal artillery.  Mounted afloat during World War II only on some older auxiliary vessels.

This gun is interesting in that, unlike most USN weapons, the nominal caliber length was actually the overall length.

This or a similar gun was also used on the Argentine battleships of the Rivadavia class.

Of built up construction and used Welin breech blocks.  The Mark 8 was built entirely out of nickel steel.


USS Maine B-10 being coaled
Note the metal shutters on the hull casemate guns

Click here for additional pictures
Gun Characteristics
Designation 6"/50 (15.2 cm) Marks 6 and 8
Ship Class Used On Maine (B-10), Virginia (B-13), St. Louis (C-20) and Pennsylvania (ACR-4) classes
Date Of Design about 1898
Date In Service 1903
Gun Weight Without breech:  18,112 lbs. (8,216 kg)
With breech:  18,628 lbs. (8,450 kg)
Gun Length oa 300.2 in (7.625 m)
Bore Length about 294 in (7.468 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist Increasing RH 0 to 1 in 25 at the muzzle
Chamber Volume 2,084 in3 (34.15 dm3)
Rate Of Fire about 6 rounds per minute
Type Bag
Projectile Types and Weights AP - 105 lbs. (47.7 kg)
Common Mark 20 Mods 0 to 4 - 105 lbs. (47.7 kg)
Anti-submarine - 105 lbs. (47.7 kg)
Illum Mark 22 Mod 1 - 95.40 lbs. (43.3 kg)
Illum Mark 23 Mods 1 and 2 - 96.0 lbs. (43.5 kg)
Bursting Charge
(see Note 2)
AP - 2.4 lbs. (1.1 kg) Explosive D
Common before and during World War I - 4.0 lbs. (1.8 kg)
Common after World War I - 7.08 lbs. (3.2 kg) Explosive D
Anti-submarine - about 26 lbs. (11.8 kg)
Projectile Length Common - 22.7 in (57.7 cm)
Propellant Charge World War I:  31 lbs. (14 kg) SPD
World War II:  38 lbs. (17.2 kg) SPD or SPDN
Muzzle Velocity 2,800 fps (853 mps)
Working Pressure 17.0 tons/in2 (2,680 kg/cm2)
Approximate Barrel Life N/A
Ammunition stowage per gun Pennsylvania and Tennessee:  200 rounds
Others:  N/A

1) During World War I, a "flat-nose" shell was developed for use against submarines.  The flat nose allowed the projectile to travel through water with reasonable accuracy.  I lack other details of this projectile.

2) Some Common rounds had a burster of 6.25 lbs. (2.8 kg).

3) AP does not appear to have been in service during World War II.

Elevation With 105 lbs. (47.7 kg) AP Shell
Range @ 14.9 degrees
With original charge
15,000 yards (13,720 m)
Range @ 15 degrees
With World War II charge
16,000 yards (14,630 m)
Armor Penetration with 105 lbs. (47.7 kg) AP Shell
Side Armor
Deck Armor
6,000 yards (5,490 m)
3.99" (101 mm)
9,000 yards (8,230 m)
2.98" (75 mm)
12,000 yards (10,970 m)
2.70" (69 mm)
Note:  Data is for face-hardened Harvey plates and is from "Ordnance Data Sheets" of 1905.
Mount / Turret Data
Designation Single Mounts
   Maine (16), Virginia (12), St. Louis (14) and Pennsylvania (14):  Mark 10
Weight  N/A
Elevation -10 / +15 degrees
Elevation Rate Manually operated, only
Train about +100 / -100 degrees
Train Rate Manually operated, only
Gun recoil N/A
Loading angle N/A

1) The Mark 10 mounting was evaluated by Admiral Charles O'Neil, chief of the Bureau of Ordnance, as being "simple and strong, all parts are accessible, it has elevating gear on both sides and friction brakes in both the elevating and training gear, it works easily, one man being able to train and elevate with facility."  However, it was apparently difficult to manufacture, with a third of the mountings being rejected by the bureau because of faulty recoil slides.

2) The hoists for these guns were electrically powered and could deliver one complete round every ten seconds to each gun.

3) The ships of the Maine class were reduced to eight guns in 1909.  The removed guns were then reused on auxiliary ships during World War I.

Data from
"Naval Weapons of World War Two" by John Campbell
"US Naval Weapons" and "U.S. Cruisers:  An Illustrated Design History" both by Norman Friedman
"Jane's Fighting Ships 1914" by Francis E. McMurtrie
"U.S. Armored Cruisers:  A Design and Operational History" by Ivan Musicant
"Battleships" by Paul Stillwell
"Naval Ordnance - A Text Book" revised in 1915 by Lt. Cmdr. Roland I. Curtain and Lt. Cmdr. Thomas L. Johnson
"Naval Staff Monographs - Home Waters Part VIII" Public Record Office, Reference ADM 186/629
"U.S. Explosive Ordnance:  Ordnance Pamphlet 1664 - May 1947" by Department of the Navy
Special help from John E. Lazauskas and Simon Schnetzke
Page History

15 August 2008 - Benchmark
03 November 2011 - Fixed typographical error