United States of America
5"/40 (12.7 cm) Marks 2, 3 and 4
Updated 10 May 2015

This was the first USN Rapid Fire (RF) gun and used mainly for battleship and cruiser secondaries.  The Mark 2 guns were too lightly built, with USS Brooklyn (ACR-3) having two of her guns bulged at the muzzle following the Battle of Santiago in 1898.  As a result, the follow on Mark 3 and Mark 4 were stronger.  Many of these guns were later modified to use the Dashiell breech mechanism, a three-motion breech that could be controlled by a single lever.

Mark 2 was constructed of tube, jacket and two hoops.  Mark 3 was nearly the same with some minor differences in the recoil cyclinders and a larger muzzle bell.  Mark 4 was similar to the Mark 3 but with a modified groove for the yoke.

One of the Mark 3 Mod 3 guns was cut down to 25 calibers and used to test anti-aircraft concepts at the proving grounds.  This led to the later development of the successful 5"/25 (12.7 cm) Mark 10 AAA weapon.


USS Olympia C-6 in 1899 flying the four-star flag of Admiral George Dewey
The 5"/40 (12.7 cm) guns are in the superstructure casemate mounts
Olympia was later rearmed with 5"/51 (12.7 cm) guns
U.S. Navy Historical Center Photograph # NH 2894


5"/40 (12.7 cm) guns aboard Auxiliary Cruiser USS Saint Paul in 1898
These are in Center-Pivot mountings
U.S. Naval Historical Center Photograph # NH 89086


5"/40 (12.7 cm) gun aboard USS Henry R. Mallory (ID-1280) in 1918-1919
This appears to be one of the later Pedestal mountings
U.S. Naval Historical Center Photograph # NH 103295


Gunner Shaw and his 5" (15.2 cm) gun on USS Raleigh (C-8)
This gun is credited with firing the first shot during the Battle of Manila Bay in 1898
Detroit Publishing Company Collection Photograph
Library of Congress Photograph ID LC-D4-20916

Gun Characteristics
Designation 5"/40 (12.7 cm) Marks 2, 3 and 4
Ship Class Used On Kearsage (B-5), Brooklyn (ACR-3), Olympia (C-6), Cincinnati (C-7) and Montgomery (C-9) classes
Date Of Design about 1890
Date In Service 1895
Gun Weight 7,000 lbs. (2,903 kg) without breech
7,080 lbs. (3,211 kg) with breech
Gun Length oa N/A
Bore Length 200 in (5.080 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist Increasing RH 0 to 1 in 25
Chamber Volume N/A
Rate Of Fire 12 rounds per minute
Type Separate
Projectile Types and Weights AP - 50 lbs. (22.7 kg)
Bursting Charge N/A
Projectile Length N/A
Propellant Charge 10 lbs. (4.5 kg) SP or SPD
Muzzle Velocity 2,300 fps (701 mps)
Working Pressure 14 tons/in2 (2,200 kg/cm2)
Approximate Barrel Life N/A
Ammunition stowage per gun Kearsage:  256 rounds
Cincinnati:  100 rounds
Others:  N/A
Elevation With 50 lbs. (22.7 kg) Shell
Range @ 30 degrees 16,000 yards (14,630 m)
Armor Penetration with 50 lbs. (22.7 kg) AP Shell
Side Armor
Deck Armor
3,000 yards (2,750 m)
2.75" (70 mm)
6,000 yards (5,490 m)
1.4" (36 mm)
Data from "U.S. Armored Cruisers" and is for KNC armor.
Mount / Turret Data
Designation Single Mountings
   Marks 2, 3 and 4:  Center-pivot
   Marks 5, 6, 7 and 8:  Pedestal Mount

Kearsage (14), Brooklyn (12), Olympia (10), Cincinnati (10) and Montgomery (8)

Weight  Mark 2:  14,198 lbs. (6,440 kg)
Mark 3:  7,850 lbs. (3,561 kg)
Marks 5, 6, 7 and 8:  About 14,500 lbs. (6,577 kg)
Elevation N/A
Elevation Rate Manual operation, only
Train Brooklyn casemates:  arc of 137 degrees
Open mounts:  about -150 / +150 degrees
Train Rate Manual operation, only
Gun recoil N/A

1) Mark 5 had an improved recoil system and a telescopic gun sight.  This mount put the elevating and training gear in the hands of the gun captain rather than with separate pointers.

2) The center-pivot mountings were difficult to adjust and had considerable amounts of bronze in their construction.  Many of these were replaced in the early 1900s with new pedestal mounts, which were of all-steel construction and far stronger.  For example, in 1901 at Cavite, Philippines, twelve new 5"/40 (12.7 cm) guns and their pedestal mounts were installed on USS Brooklyn (ACR-3).

Data from
"U.S. Battleships:  An Illustrated Design History," "US Cruisers:  An Illustrated Design History" and "US Naval Weapons" all by Norman Friedman
"U.S. Armored Cruisers:  A Design and Operational History" by Ivan Musicant
U.S. Supreme Court "Dashiell v. Grosvenor, 162 U.S. 425 (1896)" on-line at FindLaw
United States Naval Guns:  Marks and Modifications:  Service Guns - OP 127 (1916 edition) at Gene Slover's Navy Pages
Page History

12 February 2008 - Benchmark
14 February 2012 - Added constructional details and mounting Information, corrected photograph caption
10 May 2015 - Redid photograph of Olympia