Steyr Hahn, 1917, marked 38 auto


I’m looking at a 1917 dated Steyr Hahn pistol, which has been stamped ‘38 auto’ on the slide and barrel.

That smells funny, and Google has only been so helpful as to dredge up a post by Mr. John Moss from several years ago, listing several different 9x23mm cartridges. I would have sent the man a private message, but can’t figure how to do it.

I suspect the pistol in question fires the generic Austrian cartridges and was mislabeled on import, but I’m no expert.

Were these Steyr pistols ever converted to 38 auto in any real numbers, or am I correct in assuming these markings are a marketing stunt?

Thank you.


The .38 ACP, the .38Super ACP, the 9x23 Steyr, and the
9x23 Largo are all similar, but different cartridges…
The case dimensions are similar, except both.38s are Semi rimmed.
Bullet weights, powder charges, and diameters differ by a few thou’ of an inch, and the case tapers also differ…the .38s are virtually cylindrical – larger bullet.
Now the importer , not having metric ammo for the guns, could have run a .38 Auto reamer into the chamber to open it up to feed the .38 case…and the breech block face was probably tolerant enough to close on the semi rim… just like some 9mm Spanish Largo pistols will chamber .38 Super.
Or, cowboy like most importers are, just saw the similarity between.38 Super and 9mm Steyr…and ASSUMED they were the same, and marked the guns accordingly for a quick sale…similar thing was done to
Swedish 9mmBrowning Long saying they could fire .380 ACP…yes,sometimes.

BTW, the.38 Auto was Browning’s original 1902 cartridge, about the strength of a .38 Long rev. Cartridge…after WWI, the .38 Super ACP was introduced for M1911 Colt design guns…a much stronger cartridge…firing a 38 Super in a gun marked 38 auto is a road to the pearly gates.

Get the correct (9x23 Steyr) ammo and also check chamber against a .38 Auto_/ .38 SUPER case.

Safe shooting.
Doc AV


Joshua - I cannot add anything to what Doc Av posted, except about the “interchangeability” of the .38 ACP/Super cartridge case, and the 9 x 23 Steyr and 9 x 23 Bergmann Bayard cartridges, the latter called 9 mm Largo in Spain.

When researching my book on the 9 x 23 family of cartridges, I had the opportunity to try almost my entire collection of Steyr and Bergmann-Bayard cartridges in three Model 1911/1912 Steyr Hahn pistol barrels, taken out of guns owned by a friend who collected only Steyr Pistols of various models and calibers. I did not try the .38 ACP cases because they are semi-rimmed, as Doc Av said, and therefore outside of the scope of my book, which covered only the rimless versions.

The Steyr barrels accepted less than one-third of the Bergmann-Bayard cartridges, and many of the ones that would fit were late Spanish manufacture, that seemed to have slightly smaller case-diameter dimensions that earlier Spanish rounds and closer to the average case dimensions of the Steyr cartridge.

Either the gun you examined has been erroneously marked (certainly not at the factory), or has been converted to .38 ACP at some point in time. In 1917, it would be very unlikely that Waffenfabrik Steyr would have produced a prototype in that American Caliber, with WWI still with a year to go before the Armistice. It is not that weapons development does not take place during large wars; it most certainly does. But Conversion to that caliber would have signal a commercial venture, likely for the American market, and in light of the times, that makes no sense. With the post-WWI turmoil, to me it also makes no sense that the factory would be converting a 1917-dated pistol with the American or British commercial markets in mind. The .38 ACP/Super cartridge was never of much popularity except in the USA, México and to a lesser degree, in England. I believe the Steyr-Hahn pistol was discontinued sometime in 1919 or early 1920. The highest date I have ever seen on this model pistol was 1919, on a commercially-proofed one that I owned for a time.

With some exceptions, most of the above is simply my opinion, but I know of no documentation for a Steyr-Hahn pistol originally manufactured in .38 ACP caliber.

John Moss


I would advise you to pull the barrel and make a chamber casting, because placing any number of cartridges in the chamber will tell you nothing in he long run, as John M, has described.

As an example, I have a LLAMA [Mk V] marked “9MM/.38” that will chamber, feeding from the magazine:
9mm Largo, ,38 ACP, 9mm Luger, and one military marked 9mm that I am unsure of as to actual caliber/cartridge, (longer than the Luger, and not the Largo).
It will also fire the Largo, ACP, and Luger cartridges, as fed from the magazine, and cycle he slide.


Jack - the statement that trying various cartridge case types in the chamber will tell you nothing is not a correct statement. At the time I did that, many collectors (and shooters) thought the 9 mm Steyr and 9 mm Bergmann-Bayard were essentially the same cartridge except for bullet weight, just as the 9 m/m Glisenti and 9 mm Para ARE the same cartridge, except for the powder loading, with the Glisenti being, by the standards of its time, a reduced loading. Further, even though your Llama may chamber all those cartridges shows us little. The NRA, in tests for which I wish I had the “American Rifleman” issue-dates, but don’t, proved it is unsafe to fire the shorter case types (less than 23mm) in these pistols due to the different headspacing. Of course the Steyr cartridge has smaller diameter measurements than proper dimension 9 mm Bayard (Largo) cartridges, so will chamber in Bergmann-Bayard amd other models of that caliber, and likely are safe to fire in it, although I don’t recommend the practice. As mentioned, some of the later-dated 9 mm Largo rounds from Spain have dimensions more like the Steyr, perhaps by design, a question I never could get a documented answer on. The Astra 400 is even touted as handling the .380 Auto cartridge (9 mm Short) by some. Again, the NRA proved that is a dangerous practice. Handling the .38 Auto cartridge is an accident of what are, in my opinion , simply sloppy chamber and breech-face dimensions.

  There is good reason why we often see the admonition to only fire cartridges specifically made for the caliber/case type of the firearm to be used. 

  Generally speaking, the experiment of trying the two main 9 x 23 mm cartridges, Steyr and Bergmann-Bayard, was simply to test TOTAL interchangeability, which did not exist, and also a quick but admittedly unscientific and not completely accurate way to sort out the cartridges in a large collection of both calibers, since some of the headstamps were not specific and no box labels were available to reveal the intended caliber.  Exceptions in  dimensions of known cartridges proved somewhat frustrating, I will admit.

  The recommendation to pull the barrel and make a chamber cast IS a good suggestion, since the Steyr Hahn was originally made for only one case type, although some were converted by the Germans to 9 x 19 mm Para caliber, with new barrels, and the slides were marked "08" to indicate they  were for the "Patronen 08" cartridge.  A chamber cast might reveal whether or not some gunsmith had rechambered the pistol to .38 ACP, in which case marking of the new Chambering of the pistol pistol would be a very, very good idea. 

  Remember - the 9 mm/.38 marking is simply expressing the general caliber (not necessarily case type) in metric and inch measurement.  I have boxes for 9 x 19 Para cartridges from both Germany and Hungary where the caliber marking includes the designation ".38 Luger," terminology that is not generally used for the 9 mm Parabellum cartridge even in countries using the inch measurements. 

John M.


Than you gentlemen.


[quote=“JohnMoss, post:5, topic:30928”]
Jack - the statement that trying various cartridge case types in the chamber will tell you nothing is not a correct statement… Further, even though your Llama may chamber all those cartridges shows us little…[/quote]

Those are the points I was trying to make:
Just because it WILL fit in the chamber does NOT mean it IS the correct cartridge, so that does indeed not tell us which is the correct cartridge, therefor my suggestion that a chamber casting should be made to be absolutely certain of the correct cartridge.

I will give you one other example that I have seen several of:
Customer brings in a military 98, has blown cases, split at neck and shoulder.
The chamber casting told us it was rechambered to 8mm-06, and no obvious markings whatsoever on the rifles, (I believe we saw 8 or 9 of those over 20 years, mainly from the kids of WWII GIs’).
You may remember those rechamberings were done in the late 40s’ to late 50s’, because there was no 8mm Mauser ammo readily available, if at all.



You are correct, but my point was that in the case of the Steyr cartridge and the Bergmann-Bayard cartridge, in 75% of the cartridges the Bergmann would not enter the Steyr chamber. That gave us instant information that those particular cartridges were not Steyr rounds. That tells us something.

I mentioned that I felt you were correct in suggesting a chamber cast, and perhaps I would add a very close observation of the breech face and the inside surfaces of the extractor as well, to see if they had been altered. It has been a long time since I owned several Steyr-Hahn pistols as a collector, before I ever began my study of the 9 x 23 mm cartridge family which resulted in the book published by Lew Curtis. I don’t recall now if the breech face was flat, or whether it was recessed for the case head.

I remember well the problem with souvenir German (and Japanese) rifles being rechambered for available cartridges. We saw several of each in our store as well. Some of the 6.5 mm Japanese Rifles had been converted, primarily, as I recall, to the .257 Roberts cartridge. Of course the South Koreans converted relatively large quantities of 7.7 mm Japanese Arisakas to .30-06, but I believe they were clearly marked with the “new” caliber.

There are many methods, sometimes repetitious and sometimes a helpful combination, for trying to figure out anomalies like the .38"-marked Steyr of this thread. All of them tell you something; almost none of them alone tell the whole story.

Interesting conversation. I completely missed chamber casting, probably because while we took in many firearms for chamber casts to be made to determine the case type they used, we did not do gunsmithing on the store premises; Micro Sight Company originally, and then later PISCO, a California gunsmithing facility near the Nevada Border, up in the Sierras, did our work for us on contract. Our store in downtown San Francisco simply would not accomodate a repair shop.




Interesting you should mention the Japanese rifles.
Over the past five or six years I have seen two, and heard of one other, 7.7 Arisaka rifles [I do not know the models, as I was never a Japanese rifle aficianado] chambered in 7.62x39!
Our presumption was a chamber insert, as the barrels appeard to be original to the action.
Again, no markings on the rifle anywhere, and imagine our surprise when a guy cameup with a 7.7 round jammed part way into the chamber…


Badgerjack, the PRC converted many T38 rifles and carbines into 7,62x39 in the 1960s, by either rebore and re rifle rechamber or in the case of the 7,7 T99s, fitting a new chamber piece not an adaptor, to the barrel.
Occasionally SKS barrels were adapted to fit the T38 or 99 action.
The rifles all carry a Chinese character on the barrel reinforce denoting Modified.
These were all conversions done for Militia ( Min Bing)
for use up to the 1970s, and whilst the majority were done to Japanese rifles, Czech ZB 26, Brens in 7,9, etc. were also converted to AK magazines and 7,62x39.
I have not heard of other rifles…Mausers etc, being converted.

Doc AV
By the way…trying Pistol cartridges in chambers to ascertain chambering is safe to do with straight sided cases, as most pistol cases are a. Straight/ tapered sides, and headspace on mouth. The few that are semi rimmed, the .38 ACP/ Super can be distinguished by breech recess. Short cases will " fall into" a long chamber.


It may be of interest to know the chinese character for “modified”


Gǎi xìng



For the rechambered rifles, were the barrels shortened at the chamber end?


It is pretty well known that some 9x23 pistols will accept both 38 Auto and 9mm Steyr cartridges. In fact some Astra pistols are marked “9MM&38”. It seems to me that the real question here is whether the 38 Auto and the 9mm Steyr have roughly the same chamber pressure. In a quick search i couldn’t find the chamber pressure of the 9mm Steyr, but both rounds, loaded with a 115gr bullet have very similar muzzle velocities (1184fps for the 9mm Steyr and 1150 fps for the 38 Auto) indicating that the chamber pressure should be reasonably close with this load…



Lew - the real question here is whether or not a Model 1911/1912 Steyr-Hahn will accept both .38 Auto. The Steyr is a very well made pistol held to good tolerances. I cannot say that they will not accept .38 ACP rounds because I have never tried it (being semi-rimmed, the .38 ACP/
Super was outside of the parameters for our book on the 9 x 23 mm Rimless cartridges). However, published dimensions show the base dimensions of the two cartridge have an overlap of dimensions, so some .38 ACP rounds might fit, if they were not maximum dimensions. The .38 ACP OACL is slightly shorter than that of the 9 mm Steyr, and that might cause some headspacing problems in a barrel that was not specifically designed to accommodate a semi-rimmed cartridge case. Also, as mentioned before, I do not recall the breech face configuration on the Steyr pistol; that is, whether or not it would accommodate the .38 ACP semi-rim (0.400" to 0.407" head/rim diameter as opposed to Steyr dimensions of 0.376" to 0.383 inch, a very large difference).

Maybe if one of our members has a good condition Steyr Hahn and could carefully try chambering both caliber cartridges (preferable inert rounds, for safety’s sake), we could get a better idea.

My belief, by the way, is that the Spanish marking on some pistols “9mm/.38” is simply a joint metric/inch designation for the 9 mm Bergmann/Bayard cartridge. Despite the common opinion that it means “9 x 23 mm BB/.38 ACP” I have found no solid documentation for that belief. I mentioned, perhaps in another thread (couldn’t find it here) that both Hungary with the spurious Geco box, and Germany, specifically on boxes of blanks, refers to the 9 mm Parabellum cartridge also as the “.38 Luger,” another use of the metric and inch measurements together, although the latter designation is not used in any “inch-measurement countries” of which I am aware.

I spent some time in both of Antaris’ books, the one on Astra pistol and the one on Star pistols, and found no satisfactory explanation for that marking. I note, though, that some pistols made in Spain in 9 mm Corto caliber were marked “9 mm/.380 Auto” with the 9 mm, of course, referring to the 9 mm Short. That marking is clearly a case of nothing more than give both the metric and the inch designation for the SAME cartridge.

I would welcome any documentation on the marking “9mm/.38” found on Spanish pistols, as it is a question that has been argued and puzzled over all of my gun and cartridge collecting life. Perhaps some of our Spanish members could provide an absolute answer. I do not pretend to be convinced that my own opinion of the marking is correct - I think it is, but that thought is not etched in stone. The biggest factor for me is the “9 mm/.380” marking, which clearly is two designations for the same cartridge.

I would never, never fire a 9 x 19 mm cartridge in a pistol chambered for a 9 x 23 mm cartridge. Most competent authorities would agree, but unfortunately, you still see the old myth of, for instance, the Astra 400 being able to fire .380 auto, 9 mm Browning long, 9 mm Parabellum and even once in awhile, .38 Super, which is pure insanity. I would not even attempt to fire .38 Auto in a Steyr (if it fit) or an Astra 400, as the case is shorter than the Steyr or Bergmann-Bayard round, and the in the case of the Astra, the fit of the rim in the breech face is not correct. Some, with sloppy dimensions, will accept the semi-rim, but this is not by design.
Edited to add comments and to correct on spelling error
John Moss

John Moss


The CIP pressure is only 1350 bar for 9 mm Steyr while it is 2350 bar for 9 mm Luger and 2300 bar for .38 Super Automatic. In other words, 9 mm Steyr pressure is about 57 percent of the other two.
According to SAAMI data from 1992, the “ordinary” .38 Auto pressure is about 70 percent that of .38 Super Automatic (23000 versus 33000 CUP). That would mean .38 Auto develops about 23 percent (70/57) more pressure than the original 9 mm Steyr.


Thanks for the info! The 38 Auto pressure I found was 26,500psi, but I couldn’t find a 9mm Steyr pressure.
I assumed that the pistol was rechambered for 38 Auto since it was so marked, so fit was not an issue,

I would have guessed the 9mm Steyr was a higher pressure load since it was a later design than the 38 Auto.



The Japanese rifles I saw had the original barrels, with no external modifications evident, when we pulled the barreled action out of the stocks to examile them, and pull the 7.7 round out of the chamber of one of them.
The other- which I have not seen- I was told was the same, all original except for the chamber.
Had to have been drilled and an insert installed and chamber cut.
As far as I remember, both of the rifles we examined had absolutely no markings other than what you would find on a standard Japanese rifle.