9mm P.A.K stands for “Pistole Automatik Knall”, or Pistol Automatic Blank, in German. The round is a popular proprietary blank firing cartridge made for a number of blank firing handguns. In Russia, a rubber bullet variant, the 9mm P.A is legal for civilian usage. The cartridge is very popular in Turkey, where the company Atak Arms LTD, has their Zoraki line of handguns, all chambered for 9mm P.A.K. The barrels and slides are purposely made to weaker tolerances, as to not allow repeatable fire with a 9x19mm NATO cartridge. However, there are ways to work around this, and convert the black firing guns to fire live .380 ACP cartridges. This is extremely illegal in many countries as well.
This is from a machine shop in Turkey, where a machinist converts a 9mm P.A.K Beretta Cheetah blank firing clone to fire .380 ACP rounds.
This is another example of converting, by strengthening the weak slide with Steel inserts.
Then you have this video, of which the producer could easily wind up in prison for because his activities are blatantly illegal.
However, the examples below are what really caught my attention at first. The first video is with a Zoraki 2918, incidentally, doing exactly what it is supposed to be doing, when firing live ammunition, and that is the slide failing completely.
The second video appears to be a Ekol Special 99, from another Turkish company that makes blank firing handguns. This too failed (ironically in the same location that most Beretta slides fail in as well) along the slide due to the pressure of live ammunition.