Some shooters and collectors asked us something about these peculiar rounds. The Russian-based Barnaul Cartridge Plant manufactures a line of .30-06 Springfield cartridges whose cases feature a small, circular depression a few millimetres from the rim. All of Barnaul's .30-06 loads do feature it, but it only appears on .30-06 rounds, and in no other ammunition manufactured by the Russian company.
We tried to answer this question with a little bit of common sense: Barnaul uses quite un-elastic steel cases for such a long round of ammunition as the .30-06 Springfield, which is often used in vintage military-type rifles (Springfield 1903, M1 Garand and similar) that may suffer from defects such as less-than-perfect chambers or an excessive headspace. It's thus safe to assume that the Rusian company may have decided to manufacture its .30-06 Springfield shells with a slight inwards bend, so that they may lenghten a little bit should excessive pressures develop. This would prevent them from rupturing and jamming the gun.
But, according to rumors around the Web and some papers we've been submitted, that small "rim" would be nothing else but a belting, to allow the use of these rounds in a machinegun of some kind. Nonetheless, nobody has been able to positively identify the machinegun that would use them, and the only belt we could come out with that may use this kind of belting on the shells would be... the one pictured above.
What do you think about? Is the mystery solved, or is really there some kind of machinegun we don't know that's been made to use these?