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.55 Boys

December 15, 2023

The .55 Boys (13.9×99mmB in metric) is an anti-tank cartridge used by the United Kingdom in World War II. It was designed for use with the Boys Anti-Tank Rifle.

.55 Boys
TypeAnti-tank rifle cartridge
Place of originUnited Kingdom
Service history
In service1937–1945
Used byUnited Kingdom
Commonwealth of Nations
Finland, et al.
WarsWorld War II
Winter War
Continuation War
Production history
Designed1937
ManufacturerKynoch
Specifications
Parent case.50 BMG
Case typeBelted, bottleneck
Bullet diameter14.30 mm (.565 in)
Neck diameter15.392 mm (.606 in)
Shoulder diameter15.34 mm (.604 in)
Base diameter20.168 mm (.794 in)
Rim diameter20.244 mm (.797 in)
Rim thickness2.44 mm (.096 in)
Case length97.79 mm (3.85 in)
Overall length133.43 mm (5.253 in)
Ballistic performance
Bullet mass/type Velocity Energy
946 gr (61 g) Mark I 760 m/s (2,500 ft/s) 17,726 J (13,074 ft⋅lbf)
741 gr (48 g) APCR Tungsten 945 m/s (3,100 ft/s) 21,434 J (15,809 ft⋅lbf)
Test barrel length: 914.4 mm (36 inches)
Source(s): Ammo Encyclopedia, 2nd Edition by Michael Bussard

Design edit

The .55 Boys is a 13.2×99mm Hotchkiss cartridge necked up to accept a .55 caliber bullet in mid-1930s.[1] Since the shoulder of the case was narrowed, a belt was added to ensure reliably correct headspace. It performed poorly when compared to contemporary foreign anti-tank rounds, such as the German 7.92×94mm Patronen[note 1] and the Soviet 14.5×114mm rounds and, as a result, it was quickly deemed obsolete.[2]

History edit

 
.A 55 Boys cartridge (left) and a .50 BMG cartridge (right).

The concept of a small arm round for use against tanks began with the German 13.2mm TuF round, designed during World War I for use against the first British tanks.

In the 1930s, the United Kingdom began designing an anti-tank rifle to counter enemy armoured vehicles in the event of a war.

Initially the gun design was trialled using .50 inch bullet with a belted case due to lack of armour-piercing performance the calibre was increased to .55 [3]

Development on what is known as the .55 Boys was started by Captain Henry C. Boys, the Assistant Superintendent of Design at the Royal Small Arms Factory, Enfield in 1934. Boys died before the rifle was officially adopted and it was named after him. The .55 Boys round was a modified .50 BMG round necked up to accept a larger, steel-cored bullet in order to increase its armour penetration. A belt was added to reinforce the case with the heavy propellant charge.[citation needed][note 2]

The .55 Boys was adopted and manufactured alongside the Boys Anti-Tank Rifle in 1937 throughout the Commonwealth of Nations by firms such as Kynoch. When the United Kingdom entered World War II, the .55 Boys round was soon found to be insufficient against even early war Axis tanks in late 1939 and 1940.[2] However, the United Kingdom had to rely on the .55 Boys round because no better infantry anti-tank weapons were available. When the PIAT anti-tank weapon was introduced in 1943, the shaped charge it fired was far more effective against enemy armour than the .55 Boys round.[2] The Boys rifle was phased out of service on the frontline as the PIAT became the British military's primary handheld anti-tank weapon.

Although not effective as an anti-tank weapon, the .55 Boys was used until the end of World War II by British and Commonwealth countries. It also saw use during the Winter War and Continuation War by Finland. The Boys was issued to Home Guard units in the UK for use against "light armoured fighting vehicles...which the Home Guard are likely to have to deal with, certainly in the early stages of either an air-borne or sea-borne landing on our coasts." A handbook for its use noted that as well as the expected penetration of armour at various distances and angles that it would penetrate 14 inches of brick wall and 10 inches of sandbags.[4]

By the conclusion of World War II, the .55 Boys was no longer used in any major capacity.

Variants edit

The .55 Boys round went through two major variants in its lifetime, along with an experimental variant that was never adopted by the United Kingdom.

Mark I edit

This is the first variant of the .55 Boys. It uses a 926 gr (60.0 g). hardened steel core bullet with a lead sleeve, which is covered with a steel jacket. A ball and tracer version of this round was also created along with a practice round using an aluminum core in order to be more feasible for training. It has a muzzle velocity of roughly 747 m/s (2,450 ft/s).

Mark II edit

An improved loading named the Mark II was released in order to increase the round's velocity and its penetration. It generates a muzzle velocity of approximately 884 m/s (2,899.5 ft/s).[5]

At an ideal angle, the Mark 2 round was able to pierce 0.91 inches (23.2 mm) of armour at 100 yd (91 m), 0.82 inches (20.9 mm) at 300 yards (270 m) and 0.74 inches (18.8 mm) at 500 yards (460 m).[6]

APCR tungsten round edit

An experimental armour-piercing composite rigid (APCR) .55 Boys round was designed in 1942.[7] It used a tungsten core instead of a steel core, which greatly increased its penetrating ability and gave a boost to its muzzle velocity from the Mark II's 884 m/s to approximately 944 m/s (3100 ft/s). It differs from the Mark I and II rounds because of its two-part bullet. This model was never officially adopted because far better anti-tank rounds and weapons, such as the PIAT, were entering service at the time. The .55 Boys, even with a greatly improved bullet, was simply too weak to defeat the tanks being fielded by the Wehrmacht. It was however effective against the more lightly armoured tanks of the Imperial Japanese Army in the Asian and Pacific theaters up until the end of the war.

See also edit

Notes edit

  1. ^ A smaller tungsten cored round fired from a case about the same size as the Boys
  2. ^ It is incorrectly reported that the belt was added to ensure the round could not be chambered in weapons designed for the .50 BMG. though .55-calibre cartage could not be chambered in a .50-calibre weapon to begin with.
  1. ^ "British Military Small Arms Ammo - .55 inch Boys".
  2. ^ a b c Ammo Encyclopedia, Second Edition by Michael Bussard, p. 563
  3. ^ "Enfield – BSA "Boys" Anti-Tank Rifle". Historic Arms Resource Centre. from the original on 2011-11-01. Retrieved 2012-03-26.
  4. ^ Boys Anti-tank Rifle - Mark 1 1944. Gale and Polden Ltd np7
  5. ^ Bad Boys The British Rifle, Anti-Tank, .55 In, Boys[self-published source]
  6. ^ Small Arms Training Volume 1, Pamphlet No. 5 Anti-Tank Rifle 1942, HMSO
  7. ^ Williams, Anthony G (January 2013), , archived from the original on 2016-02-25, retrieved 2014-11-09

December 15, 2023
boys, 99mmb, metric, anti, tank, cartridge, used, united, kingdom, world, designed, with, boys, anti, tank, rifle, typeanti, tank, rifle, cartridgeplace, originunited, kingdomservice, historyin, service1937, 1945used, byunited, kingdom, commonwealth, nations, . The 55 Boys 13 9 99mmB in metric is an anti tank cartridge used by the United Kingdom in World War II It was designed for use with the Boys Anti Tank Rifle 55 BoysTypeAnti tank rifle cartridgePlace of originUnited KingdomService historyIn service1937 1945Used byUnited Kingdom Commonwealth of Nations Finland et al WarsWorld War II Winter War Continuation WarProduction historyDesigned1937ManufacturerKynochSpecificationsParent case 50 BMGCase typeBelted bottleneckBullet diameter14 30 mm 565 in Neck diameter15 392 mm 606 in Shoulder diameter15 34 mm 604 in Base diameter20 168 mm 794 in Rim diameter20 244 mm 797 in Rim thickness2 44 mm 096 in Case length97 79 mm 3 85 in Overall length133 43 mm 5 253 in Ballistic performanceBullet mass type Velocity Energy946 gr 61 g Mark I 760 m s 2 500 ft s 17 726 J 13 074 ft lbf 741 gr 48 g APCR Tungsten 945 m s 3 100 ft s 21 434 J 15 809 ft lbf Test barrel length 914 4 mm 36 inches Source s Ammo Encyclopedia 2nd Edition by Michael Bussard Contents 1 Design 2 History 3 Variants 3 1 Mark I 3 2 Mark II 3 3 APCR tungsten round 4 See also 5 NotesDesign editThe 55 Boys is a 13 2 99mm Hotchkiss cartridge necked up to accept a 55 caliber bullet in mid 1930s 1 Since the shoulder of the case was narrowed a belt was added to ensure reliably correct headspace It performed poorly when compared to contemporary foreign anti tank rounds such as the German 7 92 94mm Patronen note 1 and the Soviet 14 5 114mm rounds and as a result it was quickly deemed obsolete 2 History edit nbsp A 55 Boys cartridge left and a 50 BMG cartridge right The concept of a small arm round for use against tanks began with the German 13 2mm TuF round designed during World War I for use against the first British tanks In the 1930s the United Kingdom began designing an anti tank rifle to counter enemy armoured vehicles in the event of a war Initially the gun design was trialled using 50 inch bullet with a belted case due to lack of armour piercing performance the calibre was increased to 55 3 Development on what is known as the 55 Boys was started by Captain Henry C Boys the Assistant Superintendent of Design at the Royal Small Arms Factory Enfield in 1934 Boys died before the rifle was officially adopted and it was named after him The 55 Boys round was a modified 50 BMG round necked up to accept a larger steel cored bullet in order to increase its armour penetration A belt was added to reinforce the case with the heavy propellant charge citation needed note 2 The 55 Boys was adopted and manufactured alongside the Boys Anti Tank Rifle in 1937 throughout the Commonwealth of Nations by firms such as Kynoch When the United Kingdom entered World War II the 55 Boys round was soon found to be insufficient against even early war Axis tanks in late 1939 and 1940 2 However the United Kingdom had to rely on the 55 Boys round because no better infantry anti tank weapons were available When the PIAT anti tank weapon was introduced in 1943 the shaped charge it fired was far more effective against enemy armour than the 55 Boys round 2 The Boys rifle was phased out of service on the frontline as the PIAT became the British military s primary handheld anti tank weapon Although not effective as an anti tank weapon the 55 Boys was used until the end of World War II by British and Commonwealth countries It also saw use during the Winter War and Continuation War by Finland The Boys was issued to Home Guard units in the UK for use against light armoured fighting vehicles which the Home Guard are likely to have to deal with certainly in the early stages of either an air borne or sea borne landing on our coasts A handbook for its use noted that as well as the expected penetration of armour at various distances and angles that it would penetrate 14 inches of brick wall and 10 inches of sandbags 4 By the conclusion of World War II the 55 Boys was no longer used in any major capacity Variants editThe 55 Boys round went through two major variants in its lifetime along with an experimental variant that was never adopted by the United Kingdom Mark I edit This is the first variant of the 55 Boys It uses a 926 gr 60 0 g hardened steel core bullet with a lead sleeve which is covered with a steel jacket A ball and tracer version of this round was also created along with a practice round using an aluminum core in order to be more feasible for training It has a muzzle velocity of roughly 747 m s 2 450 ft s Mark II edit An improved loading named the Mark II was released in order to increase the round s velocity and its penetration It generates a muzzle velocity of approximately 884 m s 2 899 5 ft s 5 At an ideal angle the Mark 2 round was able to pierce 0 91 inches 23 2 mm of armour at 100 yd 91 m 0 82 inches 20 9 mm at 300 yards 270 m and 0 74 inches 18 8 mm at 500 yards 460 m 6 APCR tungsten round edit An experimental armour piercing composite rigid APCR 55 Boys round was designed in 1942 7 It used a tungsten core instead of a steel core which greatly increased its penetrating ability and gave a boost to its muzzle velocity from the Mark II s 884 m s to approximately 944 m s 3100 ft s It differs from the Mark I and II rounds because of its two part bullet This model was never officially adopted because far better anti tank rounds and weapons such as the PIAT were entering service at the time The 55 Boys even with a greatly improved bullet was simply too weak to defeat the tanks being fielded by the Wehrmacht It was however effective against the more lightly armoured tanks of the Imperial Japanese Army in the Asian and Pacific theaters up until the end of the war See also edit13mm caliber 14 5 114mm 12 7 108mm List of rifle cartridgesNotes edit A smaller tungsten cored round fired from a case about the same size as the Boys It is incorrectly reported that the belt was added to ensure the round could not be chambered in weapons designed for the 50 BMG though 55 calibre cartage could not be chambered in a 50 calibre weapon to begin with British Military Small Arms Ammo 55 inch Boys a b c Ammo Encyclopedia Second Edition by Michael Bussard p 563 Enfield BSA Boys Anti Tank Rifle Historic Arms Resource Centre Archived from the original on 2011 11 01 Retrieved 2012 03 26 Boys Anti tank Rifle Mark 1 1944 Gale and Polden Ltd np7 Bad Boys The British Rifle Anti Tank 55 In Boys self published source Small Arms Training Volume 1 Pamphlet No 5 Anti Tank Rifle 1942 HMSO Williams Anthony G January 2013 An Introduction to Anti Tank Cartridges archived from the original on 2016 02 25 retrieved 2014 11 09 Retrieved from https en wikipedia org w index php title 55 Boys amp oldid 1185794561, wikipedia, wiki, book, books, library,

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