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|Place of origin||USA|
|Parent case||.22 BR|
|Bullet diameter||.204 in (5.2 mm)|
|Neck diameter||.232 in (5.9 mm)|
|Shoulder diameter||.459 in (11.7 mm)|
|Base diameter||.470 in (11.9 mm)|
|Rim diameter||.473 in (12.0 mm)|
|Rim thickness||.054 in (1.4 mm)|
|Case length||1.535 in (39.0 mm)|
|Primer type||small rifle|
The .20 BR is a centerfire wildcat rifle cartridge. It is based on the .22 BR Remington case necked down to accept a 5.2 millimetres (0.204 in) diameter bullet and maintaining the shoulder angle of 30° and case length of 39 millimetres (1.535 in). The cartridge features a short fat case which is reputed to be both efficient and accurate.
The large powder capacity of the case allows it to propel a 2.6 grams (40 gr) bullet at over 1,200 metres per second (4,000 ft/s), however the cartridge is considered overbore and can be expected to have a relatively short barrel life.
Advantages of this cartridge include; its ability to be chambered in any rifle action which has the .308 Winchester sized bolt face; its short length enables action makers to utilise shorter ports to increase rigidity; and cases are easily formed and loaded.