page_title: Squeeze bore
section_title: History and usage
hierarchical_section_title: Squeeze bore / History and usage
caption_attribution_description: English: Tanks and Afvs of the British Army 1939-45 Light tank Mk VII Tetrarch Mk I with Little John adaptor
context_page_description: A squeeze bore also known as a taper-bore, sometimes cone barrel or conical barrel is a weapon where the internal barrel diameter progressively decreases towards the muzzle resulting in a reduced diameter round with an increased velocity.
context_section_description: The squeeze bore concept was first patented by German Karl Puff in 1903.  Later, Hermann Gerlich in the 1920s and 1930s experimented with the concept resulting in an experimental 7mm anti-tank rifle with a 1,800 m/s muzzle velocity.  This led to the squeeze bore concept sometimes being called the "Gerlich principle."
  Between 1939-40, Mauser-Werk AG produced the 2.8 cm sPzB 41 and Krupp (in 1941) produced the 7.5 cm Pak 41.  These were eventually discontinued due to the lack of tungsten and  manufacturing  complexity for the ammunition.
  Other uses of the squeeze bore include the British Littlejohn adaptor, a QF 6-pounder adapter and the M2 machine gun.  Squeezing down from 40mm to 30mm, 57mm to 42.6mm, and .50 caliber to .30 caliber respectively.  The Littlejohn adapter was used to extend the service life of the QF 2 pounder and was designed by František Janeček whose anglicized name gave the Littlejohn its designation.  The QF 6 pounder adapter was never adopted.
caption: A Mk VII Tetrarch Mk I with a Littlejohn adaptor.
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