German WWII 9 Para?


Exists a German cartridge WWII with denomination M20 for “gallery” use ?




I don’t know if it is a German gallery or not. In fact, without knowing the subcaliber devise, I don’t know how to tell if it is a 9mmP or a 9mmK gallery.

While we are on the subject, I have three gallery adaptor cartridges that may be pre-WWII and may be German. All three were represented as German at one time or another. I keep them in my Unknowns because I can’t even be confident that two of them are even 9mmP.

If anyone has any information on any of these I’d appreciate you sharing it.

These sub-calibers are a pretty obscure area. Is there anyone who really collects these things???

Cheers, Lew


The subcaliber rounds will drive you crazy. Unless you get them in an original package, or with the original sub-caliber kit, it is hard to tell even what caliber they represent. I have about twenty of them I have sorted by caliber, but about the only ones I am confident of, ID-wise-are the 7.65 Auto (.32 Auto) ones. Many appearing to be 9mm can also be 7.65 Luger, 9mm Kurz (.380 auto), etc. I do have a couple of 9mm Makarov ones that I know are that caliber, but that is because there is literature showing them.

I have one in 7.65 Para where the lower half of the cartridge case inserts into the upper hald with the shoulder, the upper half being a milled portion of the barrel itself. I have a 7.9 x 57 Mauser one that is 30+ inches long! It is joined with a full-length rifled barrel that goes in the original Gewehr 98 with 29.5 inch barrel.

If anyone collects these things in a big way, and really knows what caliber the pistol ones are especially, I wish they would write an article for the Forum or the IAA Journal on them, with pictures, so we could sort them out. They are NOT all obvious as to caliber, as Lew rightfully points out. A couple of those odd ones he shows could well be .30 Luger - actually more likely if they are commercial, since the 9mm caliber was restricted in many European countries. If military, it would depend on the country. My 7.65 Para with the barrel unit is Swiss, and that was the service cartridge of Switzerland for well over 40 years, officially, and used along with 9mm some more years. It could be military or commercial.

Edited only for spelling typo errors


Giovanni - I forgot to address one issue in your question. “M20” is the model number of one form of 4mm



Something to remember is that the Luger/P08 chamber design was a stepped one, intended to create a gas seal, similar to that present on it’s forebearer, the 7.65 para version.

This means that a sub-calibre insert, which follows the shape of the 9mm para cartridge can easily get stuck and would be difficult to remove. A solution, of course, is to shorten the subcalibre unit so that it’s top will not get stuck on the stepped part of the chamber.

The chamber step is located at exaclty 5 mm from the barrel end of the chamber. A 9mm para round, fired through a luger, will always show a rimmed deformation, 5 mm from the top of the cartridge, as a result of this design feature.

I’ve had a lot of fun using a laser sighter that worked by inserting it into the chamber. In the P08 it got stuck and I had to hammer it out from the barrel end with a cleaning rod.

I digitally restored a 1930s Erma subcalibre brochure a few years ago, They used a loading spoon construction for the M20 ammunition (which was popular as it could be used for indoor plinking) and a separate barrel/insert with chamber piece and replacement toggle for a full-auto .22lr version.

If we go back to 1920 we see that the first versions of the subcalibre inserts for semi-auto pistols were produced by G. Genschow & Co (GeCo) in Berlin and W. Eblen in Stuttgart. These were set up for 4mm rimfirerounds. The bore of the barrel insert was excentric of design, so that the gun’s original firing pin would touch the catridge rim. This design feature also meant that no inserts for 7,65 calibre pistols were made, as the insert’s barrel edges would be too thin.

In order to solve this problem, G. Genschow & Co and RWS constructed a new type of 4mm round which could be used as a centerfire or as a rimfire cartridge, effectively removing the need for the excentric barrel design.

RWS and GeCo both used, as Erma later on, a loading spoon for the 4mm catridges.

In the mid-1930s we also see the subcalibre inserts for hunting rifles getting more popular, like the Columbus barrel, made by Burgmuller & Sohne. It was clamped into the rifle barrel using a leaf spring fastening method. Sempert & Krieghoff also marketed a barrel insert for their hunting rifles, called the ‘Semer-Schonzeitlaufchen’ which used a separate fastening method. Both were meant for the .22lr round.
Another version was the Horrido-Einstecklauf made by Eoschke, again for the .22lr round.

Most of these sub-calibre inserts had one thing in common: They were loaded directly without the need of a separate retaining piece for the small calibre round.

An exception were the subcalibre set called ‘Champion Zimmerschiess- und Ubungsapparat’ and the ‘Rekord-Zimmerschiess-Apparat’ made by W. Glaser. This set, which was available for hunting rifles, carabines and pistols of calibres of 6,5 mm and higher, and made use of a separate retaining piece in which the subcalibre round was placed, this retaining piece was then chambered, like an ordinary round.

If we look at a 1936 RWS catalog, we see that they offer the subcalibre set with loading spoon for most pistols in 7.63, 7.65 and 9mm. Their subcalibre insert had been patented und D.R.P. 365 264 and DRGM 778716.

Pricing varied from to 6.30 RM for rifle inserts to 9.60 RM for pistol inserts.

An interesting table shows the pistols for which they can deliver inserts:
Bayard in 7.65
Bayard, model 1910 in 9mm Bergmann
Browning M1900, 1910, 1910-22 and 1920 in 7.65 and 9mm short.
Colt .32 in 7.65
Colt 1911 in .45 ACP
DWM in 7.65
Dreyse in 7.65
Frommer-Stop in 7.65 and 9mm short.
Langenhan in 7.65
Mann in 7.65
Mauser C/96 in 7.63 and 9mm Mauser Export
Mauser M30 in 7.63
Mauser M30 in 7.65
Ortgies in 7.65 and 9mm short
Parabellum in 7.65 para and 9mm para
Rheinmetall in 7.65
Sauer & Sohn M1913 and M1930 in 7.65
Savage .32 in 7.65
Star, several models, upon request.
Steyr M1911 9mm Steyr
Stock in 7.65
Walther, old model in 7.65
Walther PP and PPK in 7.65.

–Moderne Faustfeuerwaffen und ihr gebrauch, Gehard Bock, 1920.
–Waffenlexicon, Richard Mahrholdt, 1937.
–Erma subcalibre insert brochure, 1930s.
–RWS catalog, 1936.
–RWS catalog, 1922.


These show the markings left by a P08 stepped chamber. Catridges are 2005 IMI military contract.


Vlim et al. The step in the chamber of a P-08 could also be overcome by reducing the diameter of the top of the steel adaptor cartridge, as in the middle cartridge of Lew’s picture. Unfortunately, this makes the rounds look like a .30 Luger adaptor, but I suspect many of those classifed by various collectors as .30 Luger may be for the 9mm.

Between being made of thick steel, and with the very low pressure of the two different 4mm


Very interesting thread. I had not thought about the “ringed” chamber in the Luger and what it means to a subcaliber cartridge. As far as I know all but the earliest known 9mm Luger has this style chamber. The only one that doesn’t is a very early test gun for US testing, and perhaps the first 9mm Luger sent to the US for testing (IAA Journal Anniversay Issue-Geoff Sturgess article on the origin of the 9mm Para cartridge).

Anyway the ringed chamber means that the same subcaliber chamber/shape could have been used in 9mmP, 7.65mmP and perhaps 7.63mmM adaptors. The differences could have been in the barrel insert and not in the subcaliber cartridge. Would have simplified production. I think I have two post-WW2 adaptor sets which I will picture when I get home in a few weeks.

I appreciate the info from Vlim. Now I know that I don’t need to look for a subcaliber chamber for the M20!!!

Has anyone got subcaliber adaptor sets or datasheets that they could post to add to our knowledge of this area???

Again, Many thanks! Lew