The rifle above is a curious example of weapons coming full-circle and being reinvented. This is the “44 Bore” rifle, a colloquial name given to AK type rifles rechambered for the German 7.92 x 33 mm Kurz (sometimes referred to as 8 x 33 mm or 8mm Kurz) cartridge in Pakistan. How this cartridge came to be popular in the tribal areas of Pakistan is something of a mystery. According to Muhammad Yasin of the Punjab Forensic Science Agency, the Pathan tribes claim the cartridge as an indigenous development. However, the name appears to result from either the designation of the Nazi German Sturmgewehr 44 rifle (‘StG 44’), one of the weapons which originally chambered the 7.92 x 33 cartridge, or from British 7.62 x 51 mm cartridge cases bearing the “L44A2” headstamp which were commonly reformed into 7.92 x 33 dimensions.
Naming origins aside, what makes these rechambered AK type rifles interesting is that they are able to chamber and fire both the standard 7.62 x 39 mm cartridge as well as the 7.92 x 33. The bore diameter is left unchanged – 7.92 mm projectiles are simply squeezed down to 7.62 mm upon firing. This increases pressures, but not so much as to create a critical problem (though it is likely to cause headspacing issues in the weapons over time).
The chambers are reamed to accept the 7.92 x 33 cartridge, which is short enough that doing so still leaves enough intact material around the case mouth for the chamber to adequately headspace a 7.62 x 39 cartridge. The rear end of the chamber remains larger than the 7.62 x 39 case – 11.95 mm vs 11.3 mm – but the case head is held in place by the bolt face. This is unlikely to be considered as “safe practice” by many experienced shooters in other countries.
Perhaps the closest to this type of rechambering in Western use is a relatively similar technique used to rechamber .303 barrels to accept the 7.62 x 54R mm cartridge. For some owners of Bren and Vickers guns, investigating a way to use cheap and available surplus ammunition instead of the much more scarce and expensive .303 round, 7.62 x 54R was attractive since both cartridges use .311 bore diameter, and both use rimmed cases. The conversion requires running a 7.62 x 54R reamer into a .303 chamber. Both rounds headspace on the rim, but 7.62 x 54R ammo fired in such a reamed chamber will exhibit a double shoulder.
In addition to a double shoulder, a 7.62 x 39 case fired in a Pakistani 44 Bore rifle, as in the photo below, will expand all around the body of the case because of the larger diameter of the 7.92 mm chamber.