A thermal sleeve, or blanket, is a device around the length of a gun barrel of a large caliber gun, typically found on modern

tank A tank is an armoured fighting vehicle intended as a primary offensive weapon in front-line ground combat. Tank designs are a balance of heavy firepower, strong armour, and good battlefield mobility provided by tracks and a powerful engin ...

s. Its primary purpose is to provide a more consistent temperature to the

gun barrel A gun barrel is a crucial part of gun-type weapons such as small firearms, artillery pieces, and air guns. It is the straight shooting tube, usually made of rigid high-strength metal, through which a contained rapid expansion of high-pressure ...

preventing distortions due to

thermal expansion Thermal expansion is the tendency of matter to change its shape, area, volume, and density in response to a change in temperature, usually not including phase transitions. Temperature is a monotonic function of the average molecular kinetic ...

caused by the temperature differences around the barrel when firing. Thermal sleeves were originally simply insulators. They would prevent ambient conditions such as bright sunlight or winds from heating or cooling one side of a barrel more than the other which would cause a thermal distortion (bending or drooping), reducing accuracy. More modern variants contain concentric inner and outer insulating sleeves with a gap in between. Versions have been created which are detachable from a given barrel so that they can be re-used with a replacement barrel. Proposals exist for types that have advanced external thermal and radar profiles, reducing their thermal and radar signatures making the barrel and thereby the tank harder to detect.US Paten
5400691
, Rigid thermal sleeve for a gun barrel, Retrieved on 29 December 2008 One of the earliest guns to use a thermal sleeve was the

Royal Ordnance L11 The Royal Ordnance L11A5, officially designated Gun 120 mm Tk L11, is a 120 mm L/55 rifled tank gun design. It was the first of NATO's 120 mm main battle tank guns which became the standard calibre for Western tanks in the later per ...

used on the

Chieftain tank The FV4201 Chieftain was the main battle tank of the United Kingdom during the 1960s–1990s. A development of the Centurion, the Chieftain introduced the supine (reclining) driver position to British design allowing a heavily sloped hull with r ...

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Firearm components Armoured fighting vehicle equipment Artillery components {{firearms-stub