3"/50 caliber gun

The 3″/50 caliber gun (spoken "three-inch fifty-caliber") in United States naval gun terminology indicates the gun fired a projectile 3 inches (76 mm) in diameter, and the barrel was 50 calibers long (barrel length is 3 in × 50 = 150 in or 3.8 m). Different guns (identified by Mark numbers) of this caliber were used by the U.S. Navy and U.S. Coast Guard from 1890[1] through the 1990s on a variety of combatant and transport ship classes.

The gun is still in use with the Spanish Navy on Serviola-class patrol boats.

3-inch/50 caliber gun (Mk 22)
TypeNaval gun
Place of originUnited States
Service history
In service1890-1990s (US Navy)
Used byUS Navy
Production history
  • Mark 2: 1898
  • Mark 22: 1944
Produced1900 –
VariantsMarks 2, 3, 5, 6, 8, 10, 17, 18, 19, 20, 21, and 22
  • Mark 2: 2,086 pounds (946 kg) (with breech)
  • Mark 21: 1,760 pounds (800 kg)
  • Mark 2: 153.8 inches (3.91 m)
  • Mark 21: 159.7 inches (4.06 m)
Barrel length
  • Mark 2: 150 inches (380 cm) bore (50 calibres)
  • Mark 21: 150.3 inches (382 cm) bore (50 calibres)

Shell24 lb (11 kg) armor-piercing, AA, VT Frag (Variable Timing Fragmentation), Illumination 13 lb (5.9 kg)[1]
Caliber3-inch (76 mm)
  • Pedestal Mount: -10° to +15°
  • AA Mount: -10° to +85°
Rate of fire15 – 20 rounds per minute
Muzzle velocity2,700 ft/s (820 m/s)
Maximum firing range
  • 14,600 yd (13,400 m) at 43° elevation
  • 30,400 ft (9,300 m) AA ceiling
SightsPeep-site and Optical telescope

Early low-angle guns

3-inch, 50 caliber gun, World War I
An early 3"/50 on USS Rambler (SP-211), 1918.
USS Pivot firing its forward 3″/50 caliber gun.

The US Navy's first 3″/50 caliber gun (Mark 2) was an early model with a projectile velocity of 2,100 feet (640 m) per second. Low-angle (single-purpose/non anti-aircraft) mountings for this gun had a range of 7000 yards at the maximum elevation of 15 degrees. The gun entered service around 1900 with the Bainbridge-class destroyers, and was also fitted to Connecticut-class battleships. By World War II these guns were found only on a few Coast Guard cutters and Defensively Equipped Merchant Ships.[2]

Low-angle 3″/50 caliber guns (Marks 3, 5, 6, and 19) were originally mounted on ships built from the early 1900s through the early 1920s and were carried by submarines, auxiliaries, and merchant ships during the Second World War. These guns fired the same 2,700 feet (820 m) per second ammunition used by the following dual-purpose Marks, but with range limited by the maximum elevation of the mounting. These were built-up guns with a tube, partial-length jacket, hoop and vertical sliding breech block.[2]

Dual-purpose guns of the World Wars

3″/50 caliber gun aboard USS Slater

Dual-purpose 3″/50 caliber guns (Marks 10, 17, 18, and 20) first entered service in 1915 as a refit to USS Texas (BB-35), and were subsequently mounted on many types of ships as the need for anti-aircraft protection was recognized. During World War II, they were the primary gun armament on destroyer escorts, patrol frigates, submarine chasers, minesweepers, some fleet submarines, and other auxiliary vessels, and were used as a secondary dual-purpose battery on some other types of ships, including some older battleships. They also replaced the original low-angle 4"/50 caliber guns (Mark 9) on "flush-deck" Wickes and Clemson-class destroyers to provide better anti-aircraft protection. The gun was also used on specialist destroyer conversions; the "AVD" seaplane tender conversions received two guns; the "APD" high-speed transports, "DM" minelayers, and "DMS" minesweeper conversions received three guns, and those retaining destroyer classification received six.[3]

These dual-purpose guns were "quick-firing", meaning that they used fixed ammunition, with powder case and projectile permanently attached, and handled as a single unit weighing 34 pounds (as opposed to older guns and/or heavier guns, in which the shell and powder are handled and loaded separately, which reduces the weight of each handled component, but slows the loading process). The shells alone weighed about 13 pounds including an explosive bursting charge of 0.81 pounds for anti-aircraft (AA) rounds or 1.27 pounds for High Capacity (HC) rounds, the remainder of the weight being the steel casing. Maximum range was 14,600 yards at 45 degrees elevation and ceiling was 29,800 feet (9,100 m) at 85 degrees elevation. Useful life expectancy was 4300 effective full charges (EFC) per barrel.[4]

Submarine deck guns

The 3"/50 caliber gun Marks 17 and 18 was first used as a submarine deck gun on R-class submarines launched in 1918-1919. At the time it was an improvement on the earlier 3"/23 caliber gun.[5] After using larger guns on many other submarines, the 3"/50 caliber gun Mark 21 was specified as the standard deck gun on the Porpoise- through Gato-class submarines launched in 1935-1942. The small gun was chosen to remove the temptation to engage enemy escort vessels on the surface.[6] The gun was initially mounted aft of the conning tower to reduce submerged drag, but early in World War II it was shifted to a forward position at the commanding officer's option. Wartime experience showed that larger guns were needed. This need was initially met by transferring 4"/50 caliber guns from S-class submarines as they were shifted from combat to training roles beginning in late 1942. Later, the 5"/25 caliber gun, initially removed from battleships sunk or damaged in the attack on Pearl Harbor and later manufactured in a submarine version, became standard.[7]

Cold War anti-aircraft gun

Alva Laval Model 61 76mm gun
3″/50 Mk. 22 in Mk. 22 Mounting in Aalborg Maritime Museum

When multiple hits from Oerlikon 20 mm cannon and Bofors 40 mm guns were unable to prevent kamikaze strikes during the final year of the second world war; the 3"/50 was adopted as a replacement for these weapons. Post-war experimentation with an extended range variant (3"/70 Mark 26 gun) was abandoned as shipboard surface-to-air missiles were developed. The United States Navy considered contemporary 5"/38 caliber guns and 5″/54 caliber guns more effective against surface targets.

3in50 Mk 33 mount on USS Wasp (CVA-18) c1954
Mk. 33 twin mount on USS Wasp, in 1954.

The 3″/50 caliber gun (Mark 22) was a semiautomatic anti-aircraft weapon with a power driven automatic loader. These monobloc 3″ guns were fitted to both single and twin mountings. The single was to be exchanged for a twin 40 mm antiaircraft gun mount and the twin for a quadruple 40 mm mount. This was performed on Essex-class aircraft carriers, Allen M. Sumner and Gearing-class destroyers and other ships circa 1946-50. Although intended as a one-for-one replacement for the 40 mm mounts, the final version of the new 3-inch (76 mm) mounts was heavier than expected, and on most ships the mounts could be replaced only on a two-for-three basis. The mounts were of the dual purpose, open-base-ring type. The right and left gun assemblies were identical in the twin mounts. The mounts used a common power drive that could train at a rate of 30 degree/second and elevate from 15 degrees to 85 degrees at a rate of 24 degree/second. The cannon was fed automatically from an on-mount magazine which was replenished during action by two loaders on each side of the cannon.[8]

With proximity fuze and fire-control radar, a twin 3″/50 mount firing 50 rounds per minute per barrel was considered more effective than a quad Bofors 40 mm gun against subsonic aircraft,[9] but relatively ineffective against supersonic jets and cruise missiles. Destroyers that were modernized during the Fleet Rehabilitation and Modernization (FRAM) program of the 1960s had their 3-inch (76 mm) guns removed, but other ships retained them. In 1992, the 3″/50 caliber main battery on USCGC Storis was removed from the cutter. This was supposedly the last 3″/50 caliber gun in service aboard any US warship, but US Navy Charleston-class amphibious cargo ships retained their forward mounts until the last of the ships, USS El Paso (LKA-117) was decommissioned in 1994. The gun is still in service, however, on some warships of the Philippine Navy, including BRP Rajah Humabon, formerly USS Atherton.

The 17 Asheville-class gunboats mounted a single 3″/50 Mk 34 as their primary armament.

Ships mounting 3″/50 caliber guns

World War I:

World War II:

Post–World War II:

See also

  • Emblem of the United States Navy.png United States Navy portal
  • Fokker Dr. I (117710246).jpg World War I portal
  • Heinkel He 111 during the Battle of Britain.jpg World War II portal
  • Deck gun


  1. ^ a b DiGiulian
  2. ^ a b Campbell 1985 p.146
  3. ^ Silverstone 1968 pp. 112, 212, 215, 276, 303
  4. ^ Campbell 1985 p.145
  5. ^ Gardiner & Gray, p. 130
  6. ^ Friedman 1995, p. 193
  7. ^ Friedman 1995, pp. 214-219
  8. ^ "The Pouncer Challenges The Sub." Popular Mechanics, April 1955, pp. 88-93, see bottom of p. 90.
  9. ^ USN Photographic Report 9163, 1948: The New Rapid Fire Navy 8'50 and 3'50 ( You Tube- US Salem Rapid Fire Guns)
  10. ^ Albrecht 1969 p.320
  11. ^ Albrecht 1969 p.323
  12. ^ Blackman 1970 p.521
  13. ^ a b Friedman 1983, p. 221
  14. ^ Albrecht 1969 pp.322-3
  15. ^ a b Blackman 1970 p.499
  16. ^ a b Blackman 1970 p.519
  17. ^ a b c Blackman 1970 p.520
  18. ^ Albrecht 1969 p.327
  19. ^ a b Blackman 1970 p.497
  20. ^ Albrecht 1969 p.325
  21. ^ a b Blackman 1970 p.493
  22. ^ a b Blackman 1970 p.518
  23. ^ Blackman 1970 p.457
  24. ^ a b c d e Albrecht 1969 p.324
  25. ^ Blackman 1970 p.492
  26. ^ Blackman 1970 p.496
  27. ^ Blackman 1970 p.456
  28. ^ Blackman 1970 p.529
  29. ^ Blackman 1970 p.522
  30. ^ Blackman 1970 p.495
  31. ^ Blackman 1970 p.523
  32. ^ Blackman 1970 p.498
  33. ^ Blackman 1970 p.490


  • Albrecht, Gerhard (1969). Weyer's Warships of the World 1969. Annapolis, Md.: Naval Institute Press.
  • Blackman, Raymond V. B. (1970). Jane's Fighting Ships 1970-71. Jane's Yearbooks.
  • Campbell, John (1985). Naval Weapons of World War Two. Annapolis, Md.: Naval Institute Press. ISBN 0-87021-459-4.
  • Friedman, Norman (1983). U.S. Aircraft Carriers: An Illustrated Design History. Annapolis, MD: Naval Institute Press. ISBN 0-87021-739-9.
  • Friedman, Norman (1995). U.S. Submarines Through 1945: An Illustrated Design History. Annapolis, Md.: United States Naval Institute. ISBN 1-55750-263-3.
  • Gardiner, Robert; Gray, Randal (1985). Conway's All the World's Fighting Ships, 1906-1921. London: Conway Maritime Press. ISBN 0-85177-245-5.
  • Silverstone, Paul H. (1968). U.S. Warships of World War II. Doubleday and Company.
  • DiGiulian, Tony, United States of America 3″/50 (7.62 cm) Marks 10, 17, 18, 19, 20, 21 and 22

External links

.50 BMG

The .50 Browning Machine Gun (.50 BMG, 12.7×99mm NATO and designated as the 50 Browning by the C.I.P.) is a cartridge developed for the Browning .50 caliber machine gun in the late 1910s, entering official service in 1921. Under STANAG 4383, it is a standard cartridge for NATO forces as well as many non-NATO countries. The cartridge itself has been made in many variants: multiple generations of regular ball, tracer, armor-piercing (AP), incendiary, and saboted sub-caliber rounds. The rounds intended for machine guns are made into a continuous belt using metallic links.

The .50 BMG cartridge is also used in long-range target and anti-materiel rifles, as well as other .50-caliber machine guns.

A wide variety of ammunition is available, and the availability of match grade ammunition has increased the usefulness of .50 caliber rifles by allowing more accurate fire than lower quality rounds.

12.7 cm/50 Type 3 naval gun

The 12.7 cm/50 Type 3 naval gun was a medium calibre naval gun of the Imperial Japanese Navy used during World War II. It was the standard weapon for Japanese destroyers between 1928 and 1944 (except Akizuki and Matsu classes). It has been credited as a true dual-purpose gun, but this was more a nominal capability than real, as its bag propellant and need for hand ramming required the gun to be loaded at elevation angles of 5–10°. This dropped its rate of fire to a relatively slow 5–10 rounds per minute, and its training speed of only 6° per second meant that it had a great deal of difficulty engaging enemy aircraft with any chance of success. After the end of World War II the gun remained in service on the two Japanese destroyers ceded to the Soviet Union and the Republic of China as war reparations.

14"/45 caliber gun

The 14"/45 caliber gun, (spoken "fourteen-inch-forty-five-caliber"), whose variations were known initially as the Mark 1, 2, 3, and 5, and, when upgraded in the 1930s, were redesignated as the Mark 8, 9, 10, and 12. They were the first 14-inch (356 mm) guns to be employed with the United States Navy and were, for over a year, the most powerful naval ordnance afloat. The 14-inch/45 caliber guns were installed as the primary armament aboard all of the United States Navy's New York-class, Nevada-class, and Pennsylvania-class battleships. The gun also saw service in the British Royal Navy, where it was designated the BL 14 inch gun Mk II.

14"/50 caliber gun

The 14"/50 caliber gun was a naval gun mounted on New Mexico and Tennessee-class battleships. These ships also featured the first "three-gun" turrets, meaning that each gun in each turret could be "individually sleeved" to elevate separately (however, they could be linked so they would elevate as a unit, similar to the triple turrets on other Navy ships). The 14"/50 caliber guns were designated as Mark 4 and 6, with later versions known as Mark 7, 11, and B. These guns were more powerful than the main gun mounted on the previous three classes of US battleships (the New York, Nevada and Pennsylvania classes), the 14"/45 caliber gun.

16"/50 caliber M1919 gun

The 16 inch Gun M1919 (406 mm) was a large coastal artillery piece installed to defend the United States' major seaports between 1920 and 1946. It was operated by the United States Army Coast Artillery Corps. Only a small number were produced and only seven were mounted; in 1922 and 1940 the US Navy surplussed a number of their own 16-inch/50 guns, which were mated to modified M1919 carriages and filled the need for additional weapons.

16"/50 caliber Mark 2 gun

The 16"/50 caliber Mark 2 gun and the near-identical Mark 3 were guns originally designed and built for the United States Navy as the main armament for the South Dakota-class battleships and Lexington-class battlecruisers. At the time, they were among the heaviest guns built for use as naval artillery.As part of the Washington Naval Treaty of 1922, both of these ship classes were cancelled part way through construction, surplussing about 70 examples of the 16-inch/50 which had already been built. Twenty were released to the US Army, between 1922–1924, for use by the Coast Artillery Corps, the rest were kept in storage for future naval use. Only ten of the twenty available guns were deployed (in five two-gun batteries) prior to 1940.When the design of the Iowa-class battleship began in 1938, it was initially assumed these ships would use the surplus guns. However, due to a miscommunication between the two Navy departments involved in the design, the ships required a lighter gun than the Mark 2/Mark 3, resulting, ultimately, in the design of the 267,900 lb (121,500 kg) 16"/50 caliber Mark 7 gun. In January 1941 all but three of the remaining fifty Mark 2 and Mark 3 guns were released to the Army. They were the primary armament of 21 two-gun batteries built in the United States and its territories during World War II. However, none of these were fired in anger.

16"/50 caliber Mark 7 gun

The 16"/50 caliber Mark 7 – United States Naval Gun was the main armament of the Iowa-class battleships.

3"/23 caliber gun

The 3"/23 caliber gun (spoken "three-inch-twenty-three-caliber") was the standard anti-aircraft gun for United States destroyers through World War I and the 1920s. United States naval gun terminology indicates the gun fired a projectile 3 inches (76 mm) in diameter, and the barrel was 23 calibers long (barrel length is 3" x 23 = 69" or 1.75 meters.)

4"/50 caliber gun

The 4"/50 caliber gun (spoken "four-inch-fifty-caliber") was the standard low-angle, quick-firing gun for United States, first appearing on the monitor Arkansas and then used on "Flush Deck" destroyers through World War I and the 1920s. It was also the standard deck gun on S-class submarines, and was used to rearm numerous submarines built with 3-inch (76 mm) guns early in World War II. United States naval gun terminology indicates the gun fired a projectile 4-inch (102 mm) in diameter, and the barrel was 50 calibers long.

5"/50 caliber gun

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.

5"/51 caliber gun

5"/51 caliber guns (spoken "five-inch-fifty-one-caliber") initially served as the secondary battery of United States Navy battleships built from 1907 through the 1920s, also serving on other vessels. United States naval gun terminology indicates the gun fired a projectile 5-inch (127 mm) in diameter, and the barrel was 51 calibers long.

6"/50 caliber gun

The 6"/50 caliber gun Mark 6 and Mark 8 (spoken "six-inch-fifty-caliber") were used for the secondary batteries of the United States Navy's Maine-class and Virginia-class battleships, as well as the Pennsylvania-class and Tennessee-class armored cruisers. They were also used as the main battery on the St. Louis-class protected cruisers.

7"/44 caliber gun

The 7"/44 caliber gun Mark 1 (spoken "seven-inch-forty-four--caliber") and 7"/45 caliber gun Mark 2 (spoken "seven-inch-forty-five--caliber") were used for the secondary batteries of the United States Navy's last generation of pre-dreadnought battleships, the Connecticut-class and Mississippi-class. The 7-inch (178 mm) caliber was considered, at the time, to be the largest caliber weapon sutiable as a rapid-fire secondary gun because its shells were the heaviest that one man could handle alone.


In guns, particularly firearms, caliber or calibre is the approximate internal diameter of the gun barrel, or the diameter of the projectile it shoots. It is measured in hundredths or thousandths of an inch or in millimetres. For example, a ".45 caliber" firearm has a barrel diameter of roughly 0.45 inches (11 mm). Barrel diameters can also be expressed using metric dimensions. For example, a "9 mm pistol" has a barrel diameter of about 9 millimetres (it is rare for the actual barrel diameter to precisely match the designation however, and the bullet itself is yet another dimension). When the barrel diameter is given in inches, the abbreviation "cal" (for "caliber") can be used. For example, a small-bore rifle with a diameter of 0.22 inches (5.6 mm) can be referred to as a ".22" or ".22 cal"; however, the decimal point is generally dropped when spoken, making it a "twenty-two" or a "two-two caliber". A ".45 caliber" would be a "forty-five", or "four-five caliber", etc.

In a rifled barrel, the distance is measured between opposing lands or grooves; groove measurements are common in cartridge designations originating in the United States, while land measurements are more common elsewhere in the world. Good performance requires a bullet to closely match the groove diameter of a barrel to ensure a good gas seal and hence maximal bullet propulsion.

While modern firearms are generally referred to by the name of the cartridge the gun is chambered for, they are still categorized together based on bore diameter. For example, a firearm might be described as a "30 caliber rifle", which could be any of a wide range of cartridges using a roughly 0.30 inches (7.6 mm) projectile; or a "22 rimfire", referring to any rimfire firearms firing cartridges with a .22 caliber projectile.

Firearm calibers outside the range of .17–.50 inches (4.3–12.7 mm) exist, but are rarely encountered. Wildcat cartridges, for example, can be found in .10, .12, and .14 cal (2.5, 3.0, and 3.6 mm), typically used for short-range varmint hunting, where the high-velocity, lightweight bullets provide devastating terminal ballistics with little risk of ricochet. Larger calibers, such as .577, .585, .600, and .700 (14.7, 14.9, 15.2, 17.8 mm) are generally found in proprietary cartridges chambered in express rifles or similar guns intended for use on dangerous game. The .950 JDJ is the only known cartridge beyond 70 caliber used in a rifle.

Referring to artillery, "caliber" is used to describe the barrel length as multiples of the bore diameter. A "5-inch 50 calibre" gun has a bore diameter of 5 in (12.7 cm) and a barrel length of 50 times 5 in = 250 in (6.35 m). The main guns of USS Missouri, an Iowa-class battleship, are 16" 50 caliber.

In shotguns, each gauge of shotgun has a set caliber. For example, a 12 gauge shotgun has a caliber of 18.53 mm or .729 inches.

Caliber (artillery)

In artillery, caliber or calibre is the internal diameter of a gun barrel, or by extension a relative measure of the length.

M2 Browning

The M2 Machine Gun or Browning .50 Caliber Machine Gun is a heavy machine gun designed toward the end of World War I by John Browning. Its design is similar to Browning's earlier M1919 Browning machine gun, which was chambered for the .30-06 cartridge. The M2 uses the much larger and much more powerful .50 BMG cartridge, which was developed alongside and takes its name from the gun itself (BMG standing for Browning Machine Gun). It has been referred to as "Ma Deuce", in reference to its M2 nomenclature. The design has had many specific designations; the official designation for the current infantry type is Browning Machine Gun, Cal. .50, M2, HB, Flexible. It is effective against infantry, unarmored or lightly armored vehicles and boats, light fortifications and low-flying aircraft.

The Browning .50 caliber machine gun has been used extensively as a vehicle weapon and for aircraft armament by the United States from the 1930s to the present. It was heavily used during World War II, the Korean War, the Vietnam War, the Falklands War, the Soviet–Afghan War, the Gulf War, the Iraq War and the War in Afghanistan in the 2000s and 2010s. It is the primary heavy machine gun of NATO countries, and has been used by many other countries as well. The M2 has been in use longer than any other firearm in U.S. inventory except the .45 ACP M1911 pistol, also designed by John Browning.

The current M2HB is manufactured in the U.S. by General Dynamics and U.S. Ordnance for use by the U.S. government, and for allies via Foreign Military Sales, as well as foreign manufacturers such as FN Herstal.

New Mexico-class battleship

The New Mexico-class battleships of the United States Navy, all three of whose construction began in 1915, were improvements on the design introduced three years earlier with the Nevada class.

The twelve-gun main battery of the preceding Pennsylvania class was retained, but with longer 14-inch (356 mm)/50 caliber guns in improved triple turrets. Hull design was also upgraded with a 'clipper' bow for better seakeeping and a sleeker look. One ship, New Mexico, was fitted with turbo-electric propulsion.

Though eight secondary battery guns were located in extremely wet bow and stern positions and were soon removed, the rest of the ships' 5-inch (127 mm)/51 caliber guns were mounted in the superstructure, a great improvement over earlier U.S. Navy battleships' arrangements.

QF 12-pounder 12 cwt naval gun

The QF 12-pounder 12-cwt gun (abbreviated as Q.F. 12-pdr. (12-cwt.)) was a common, versatile 3-inch (76.2 mm) calibre naval gun introduced in 1894 and used until the middle of the 20th century. It was produced by Armstrong Whitworth, Elswick and used on Royal Navy warships, exported to allied countries, and used for land service. In British service "12-pounder" was the rounded value of the projectile weight, and "12 cwt (hundredweight)" was the weight of the barrel and breech, to differentiate it from other "12-pounder" guns.

As the Type 41 3-inch (76.2 mm)/40 it was used on most early battleships and cruisers of the Imperial Japanese Navy, though it was commonly referred to by its UK designation as a "12-pounder" gun.

QF 3-pounder Hotchkiss

The QF 3-pounder Hotchkiss or in French use Canon Hotchkiss à tir rapide de 47 mm were a family of long-lived light 47 mm naval guns introduced in 1886 to defend against new, small and fast vessels such as torpedo boats and later submarines. There were many variants produced, often under license which ranged in length from 32 to 50 calibers but 40 caliber was the most common version. They were widely used by the navies of a number of nations and often used by both sides in a conflict. They were also used ashore as coastal defense guns and later as an anti-aircraft gun, whether on improvised or specialized HA/LA mounts.

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