Should see the lengthwise photo of theis blank:
9mm PAK ( Pistole-Automatische-Knall) is a 9x22 case with a Plastic charge insert, roll crimped into the mouth of the case; the plastic “bubble” bursts on firing, and this causes the shell to be ejected.
The case is the same diameter as a .223 case ( .375-8 ") to prevent chambering a “real” 9mm Parabellum Manovre Patrone. (.390-.395 head); other similar case is the M1907 Browning (Swede) 9mm Long
The 9mm PAK is a recent “invention” ( 1990s-early 2000) for a range of “Imitation” Die cast metal Automatic Pistols made by several European makers ( “Bruni srl”, Milan and also Turkish “Replica makers.”)
Prior to that, there were only 9x17 Knall ( Revolver and starting Gun blanks–RWS/DAG) and the 8mm Gas-Pistole/ Alarm-Pistole cartridge ( a 7,65x19 Blank ( plastic insert, rolled mouth) for Imitation guns.
The dimensional differances supposedly prevent the interchange with Real Blanks (which would be disastrous in the weak, direct blowback, soft metal replicas) but confusion still exists in a lot of Markets, where before 9mm Real Blanks ( 9x19 extended neck) were and are available… at least Several times a year, our company has got to go thru a long discussion with customers wanting “9mm Blanks” as to what they realy want…9mm revolver Knall (Rimmed) or 9mm PAK or 9mm Parabellum for real guns…and some customers are still confused…until they find the “9mm Blanks” they bought from other suppliers have either not worked , Not chambered, or if they have, blown the gun up!!!.
Armscor of the Philippines (Not “Armscorp” etc) does make 9mm PAK and 9x19 Parabellum Blanks, as the market requires. (personal contact).
AV Ballistics Film Ordnance Services