Czech "necked" 9x19mm


#1

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?


#2

The “necking” looks uneven to me. How would this round properly headspace in a normal 9x19mm chamber with such a dramatic reduction in its case mouth diameter?

Seems like there would be many other ways to crimp the bullet in place more securely to achieve the desired result.

AKMS


#3

I didn’t design or manufacture it. Only have the round and the explaination that came with it.

I agree that the shoulder does look uneven in the photo, but it is actually pretty even on the round.

Perhaps the case taper is sufficient to headspace. Not a high pressure load so I’m not sure headspace is important as long as the round is firmly enough in position to fire.

Cheers,

Lew


#4

Firstly, it looks as if it has been crimped by running the loaded 9mm cartridge into a 7,62x25 Die, which gives a “crimp” equal to the normal “Bullet diameter”
( a method we use to make 9mm Full Profile Blanks from either 9x29 (9mm Magnum) or 5,56 cases (trimmed and expanded to give the proper 9mm case mouth diameter).

If it is a “proof round”, then either it is for reference purposes ( in a pressure test gun) or for testing 9mm Pistol barrels ( where in it is “hand fed” to the chamber, and does not necessaraly require “mechanical feeding” from the magazine.

IN either case, the heavy crimp will raise the chamber pressure, but I don’t think sufficiently to cause a “proof pressure” situation. It may be an attempt to record pressure excursions with excessive crimping, or some other “in House” test or experiment, related to manufacturing processes.

Interesting cartridge. WE may never know the reason…it may be a manufacturing mistake, of course ( wrong crimp die??)

regards,
Doc AV
AV Ballistics Film Ordnance Services.