out over time, the API blowback design results in reduced recoil. According to Anthony G. Williams, the "API blowback principle is used virtually in all open bolt sub-machine guns" (technically, although generally these are known as "simple blowback" weapons due to the very late ignition of the cartridge compared to specially designed API blowback guns like the MK 108), although "the relatively low pressures and velocities mean that extended chambers and rebated-rim cartridges are not required" for sub-machine guns. An example of API in sub-machine guns is the L2A3 Sterling submachine gun, where the maximum chamber pressure is achieved while the breechblock is still moving forward and is about 0.46 mm away from the rear face of the chamber. In heavier weapons, advanced primer ignition (API) was originally developed by Reinhold Becker for use on the Becker Type M2 20 mm cannon. It became a feature of a wide range of designs that can be traced back to Becker's, including the Oerlikon cannon widely used as anti-aircraft weapons during World War II. To increase performance of API blowback firearms, larger calibre APIB guns such as the Becker and Oerlikon use extended chambers, longer than is necessary to contain the round, and ammunition for APIB firearms come with straight-sided cartridges with rebated rims (rims that are smaller in diameter than the cartridge itself). The last part of forward motion and the first part of the rearward motion of the case and bolt happen within the confines of this extended chamber. As long as the gas pressure in the barrel is high, the walls of the case remain supported and the breach sealed, although the case is sliding rearwards. This sliding motion of the case, while it is expanded by a high internal gas pressure, risks tearing it apart, and a common solution is to grease the ammunition to reduce the friction. The case needs to have a rebated rim because the front end of the bolt will enter the chamber, and the extractor claw hooked over the rim therefore has to fit also within the diameter of the chamber. The case generally has very little neck, because this remains unsupported during the firing cycle and is generally deformed; a strongly necked case would be likely to split. The API blowback design permits the use of more powerful ammunition in a lighter gun than would be achieved by using simple blowback, and