While digging through the collection to answer a previous thread, I ran across a cartridge I wanted to ask about. It looks like a normal 9x19mm, except it has a very distinctive neck. The headstamp is the common SBP 9mmP.
The bullet diameter at the case mouth is 8.95mm (normal for 9x19mm ammo)
The case diameter just 1mm below the casemouth is 9.20mm while on a normal 9x19mm by S&B it is about 9,52mm.
The case is straight back to the shoulder rather than tapered like a normal 9x19mm
Just behind the shoulder the case diameter is 9.66mm while the S&B load I used for comparison is slightly smaller (9.63mm).
Both cartridges have the same case length but the length of this cartridge is much shorter at 27.3mm verse the normal 29,46mm.
The note I have on this round is that it is a proof load and the “neck” is to lock the bullet in place and to cause a pressure spike.
Has anyone seen something similar? Is there any documentation of this type of “proof” load?