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==Ammunition==
==Ammunition==
[[File:20poundercartridgecasewithHEshell.jpg|thumb|20 pdr [[British ordnance terms#HE|HE]] [[British ordnance terms#Round|round]]]]
[[File:20poundercartridgecasewithHEshell.jpg|thumb|20 pdr [[British ordnance terms#HE|HE]] [[British ordnance terms#Round|round]]]]
*'''Shot Mk. 1''' : an Armour-Piercing Capped Ballistic Capped (APCBC) round.
*'''APDS Mk. 1''' : an [[Armour-piercing discarding sabot|Armour-Piercing Discarding Sabot]] round. It uses a [[Nitrocellulose|nitrocellulose]] propellant (NH). The APDS Mk. 1 was fielded in 1947.
*'''DS/T PRAC Mk. 2''' : a training variant of the APDS Mk. 1, it is identifiable by the yellow band painted on its black lead sabot. It uses a [[Cordite|cordite]] propellant (WM).
*'''APDS-T Mk. 3''' : an improved Armour-Piercing Discarding Sabot round fitted with tracer. The APDS-T Mk. 3 was fielded in 1950.
*'''DS/T PRAC Mk. 4''' : a training variant of the APDS-T Mk. 3 except for mild steel sabot painted black with yellow band. The DS/T PRAC Mk. 4 was fielded in 1955.
*'''Shell Mk. 1''' : an [[Shell (projectile)|High-Explosive (HE) shell]] using a No. 410 Mk. 1 instantaneous [[Fuze|fuze]]. The shell is painted olive drab or buff with red band and black RDX/BWX (explosive filler).
*'''SMK BE Mk. 1''' : a [[smoke shell]] filled with three internal smoke canisters ejected by a Base Ejection (BE) device.
*'''CAN''' : a [[Canister shot|canister shot]] consisting of a black metal cylinder filled with 580 steel pellets (9.5&nbsp;kg). It has an effective range of 229&nbsp;m<ref>{{cite web |title=Centurion Mk.3/5/7/8 - 20 Pounder ammunition |url=https://i.imgur.com/pzPYk0J.jpeg |access-date=12 November 2022 |archive-url=https://web.archive.org/web/20221112105734/https://i.imgur.com/pzPYk0J.jpeg |archive-date=12 November 2022 |date=12 November 2022}}</ref>.


{|class="wikitable"
{|class="wikitable"
|-
|-
!Designation
!Round
!Weight, complete round
!Projectile weight
!Muzzle velocity{{sfnp|Norman|1967|p=12}}
!Muzzle velocity{{sfnp|Norman|1967|p=12}}
|-
|-
|Shot Mk. 1
⚫
|APDS
|/
⚫
|{{convert|4,700|ft/s|m/s|abbr=on}}
|9.1&nbsp;kg
⚫
|{{convert|1000|m/s|ft/s|abbr=on}}
|-
|-
⚫
|APDS Mk. 1
|HE
|/
⚫
|{{convert|1,975|ft/s|m/s|abbr=on}}
|/
⚫
|{{convert|1400|m/s|ft/s|abbr=on}}
|-
|-
|APDS-T Mk. 3
|Canister
|17&nbsp;kg
⚫
|{{convert|3,000|ft/s|m/s|abbr=on}}
|3.2&nbsp;kg
⚫
|{{convert|1465|m/s|ft/s|abbr=on}}
|-
|-
|Shell Mk. 1
|Smoke
|17&nbsp;kg
⚫
|{{convert|825|ft/s|m/s|abbr=on}}
|7.5&nbsp;kg
⚫
|{{convert|602|m/s|ft/s|abbr=on}}
|-
|SMK BE Mk. 1
|18&nbsp;kg
|9.3&nbsp;kg
|{{convert|251|m/s|ft/s|abbr=on}}
|-
|CAN
|22.5&nbsp;kg
|9.5&nbsp;kg
|{{convert|910|m/s|ft/s|abbr=on}}
|}
|}


Revision as of 11:08, 12 November 2022

Ordnance QF 20 pounder Mark I
Charioteer tank equipped with the 20 pounder. This gun is a later model which is fitted with a bore evacuator
TypeTank gun
Place of originUnited Kingdom
Service history
In service1948–1976
Used byUnited Kingdom
Australia
Austria
Canada
Finland
Israel
Jordan
Lebanon
South Africa
WarsKorean War
Vietnam War
Six-Day War
South African Border War
Specifications
Length226.4 in (5.75 m), 66.7 calibres
Shell84×618mm R
Calibre84 millimetres (3.31 in)
Elevation+18 to −10 in Centurion Mk 5

The Ordnance QF 20 pounder (known as 20 pounder, 20 pdr or simply 20-pr) was a British 84 mm (3.307 inch) tank gun.[1][i] It was introduced in 1948 and used in the Centurion main battle tank, Charioteer medium tank, and Caernarvon Mark II heavy tank. After the 20 pounder gun was found to have inadequate performance against the Soviet T-54 the gun was mostly replaced in service by the larger calibre 105 mm L7 gun.

Design and development

The gun was developed by the Royal Ordnance Factories.

As fitted to the Charioteer, it ran through two models:

  • Model A without a fume extractor.
  • Model B with a fume extractor.

The L7 105 mm tank gun was developed from the 20 pounder. In 1954, the original version of the 105 mm was made by re-boring the tube of a 20 pounder barrel.[2]

Service history

The gun was fitted predominantly to the Centurion tank, seeing action with British and Australian forces during the Korean and Vietnam War. When a Soviet T-54A main battle tank was driven to the British embassy in Budapest by Hungarian rebels during the Hungarian Revolution of 1956, analysis of its armour and 100 mm gun led British officials to determine that the 20 pounder was ineffective at defeating Soviet armour. This led to the development of the 105 mm L7 tank gun, which was designed to fit specifically into the turret mountings of the 20 pounder, facilitating for easily upgunning existing tanks equipped with the 20 pounder.[3]

One 20 pounder gun was fitted to a Swiss pre-production Panzer 58, replacing a domestic 90 mm Kanone 1948 gun, before it was equipped with the 105 mm L7.[4]

Performance

The 20 pounder's APCBC projectile had an initial muzzle velocity of 1,020 metres per second and could penetrate 210 mm (8.3 in) of rolled homogeneous armour (RHA). However, these conventional rounds were rarely used.

The APDS projectile had a muzzle velocity of 1,465 m/s (4,810 ft/s) and the APDS Mk.3 shell could penetrate 330 mm (13 in) of RHA at a distance of 1,000 yards (910 m), and 290 mm (11 in) of penetration at 2,000 yards (1,800 m), equating to a line of sight penetration of 330 mm and 290 mm respectively.[5][ii] Against sloped armour, the APDS had reduced effectiveness: penetrating 87 mm (3.4 in) and 77 mm (3.0 in) of RHA at 1,000 yd (910 m) and 2,000 yd (1,800 m) respectively, against a plate angled 60 degrees from the normal, this is only 174 mm (6.9 in), and 154 mm (6.1 in) of line of sight penetration.[6] At given ranges, the 20 pounder APDS Mk. III shot only had 53% of its line of sight penetration against a sloped plate, compared to at the normal. Line of sight penetration refers to a flat line drawn through a piece of sloped armour, indicating the effective thickness.

The 20-pounder could also fire high-explosive and canister shot shells.

Ammunition

20 pdr HE round
  • Shot Mk. 1 : an Armour-Piercing Capped Ballistic Capped (APCBC) round.
  • APDS Mk. 1 : an Armour-Piercing Discarding Sabot round. It uses a nitrocellulose propellant (NH). The APDS Mk. 1 was fielded in 1947.
  • DS/T PRAC Mk. 2 : a training variant of the APDS Mk. 1, it is identifiable by the yellow band painted on its black lead sabot. It uses a cordite propellant (WM).
  • APDS-T Mk. 3 : an improved Armour-Piercing Discarding Sabot round fitted with tracer. The APDS-T Mk. 3 was fielded in 1950.
  • DS/T PRAC Mk. 4 : a training variant of the APDS-T Mk. 3 except for mild steel sabot painted black with yellow band. The DS/T PRAC Mk. 4 was fielded in 1955.
  • Shell Mk. 1 : an High-Explosive (HE) shell using a No. 410 Mk. 1 instantaneous fuze. The shell is painted olive drab or buff with red band and black RDX/BWX (explosive filler).
  • SMK BE Mk. 1 : a smoke shell filled with three internal smoke canisters ejected by a Base Ejection (BE) device.
  • CAN : a canister shot consisting of a black metal cylinder filled with 580 steel pellets (9.5 kg). It has an effective range of 229 m[7].
Designation Weight, complete round Projectile weight Muzzle velocity[8]
Shot Mk. 1 / 9.1 kg 1,000 m/s (3,300 ft/s)
APDS Mk. 1 / / 1,400 m/s (4,600 ft/s)
APDS-T Mk. 3 17 kg 3.2 kg 1,465 m/s (4,810 ft/s)
Shell Mk. 1 17 kg 7.5 kg 602 m/s (1,980 ft/s)
SMK BE Mk. 1 18 kg 9.3 kg 251 m/s (820 ft/s)
CAN 22.5 kg 9.5 kg 910 m/s (3,000 ft/s)

Footnotes

Notes

  1. ^ The gun is specified as 83.4 mm (3.283 in) here, while Ogorkiewiecz states the weapon was 83.8 mm. Norman gives it as "3.3 inch (84 mm)"
  2. ^ The 20 pounder's APDS round had twice the penetration capability of an KwK 36 8.8 cm AP round.

References

  1. ^ Pugh (1962), p. 34.
  2. ^ Ogorkiewicz (1991), p. 70.
  3. ^ Zaloga, Steve, 1952- (2004). T-54 and T-55 main battle tanks 1944-2004. Johnson, Hugh, 1971-. Oxford: Osprey. ISBN 1841767921. OCLC 60834392.{{cite book}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
  4. ^ Ford (1997), p. 121.
  5. ^ Dunstan (2003), p. 10.
  6. ^ British Army Operational Research Group (June 1954), Memorandum E.13 Tank Effectiveness: Conqueror, Conway and Charioteer, p. 9 – via Archive.org
  7. ^ "Centurion Mk.3/5/7/8 - 20 Pounder ammunition". 12 November 2022. Archived from the original on 12 November 2022. Retrieved 12 November 2022.
  8. ^ Norman (1967), p. 12.

Bibliography

See also

Wikimedia Commons has media related to QF 20 pounder.
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