.38 Super question

I read something on another forum suggesting that the early .38 ACP and .38 Super cartridges used .360-.361 diameter bullets. If so, when did the change to .355-.356 occur? I thought it was always the latter from the beginning for both.

Dennis - I just measured about 40 specimens at random, various countries and makers, of .38 A.C.P. (today called .38 Auto) and .38 Super (Today called .38 Super Auto +P or something like that). I measured the bullets at the case mouth. All eras of production were covered including the very first UMC round made in 1900 and headstamped “U.M.C. .38 C.A.,” a fairly scarce headstamp. Measurements ran from .354" to .357" with one foreign round measuring .353", which could be an anomoly, or it could be a reflection of bullet taper not ending above the case mouth. I found no evidence of any particular change in diameter of the bullet from the earliest UMC and Winchester rounds, until the present. There were variations as noted, of course.

Interestingly, though, UMC, for which I have the best production information, and who began making the .38 A.C.P. cartridge in 1900 as noted above, had an entry as early as January 31, 1903, indicating the had increased the size of the soft-point bullet, in the interests of better accuracy, to a minimum size of .359" and a maximum of .360". However, even though I had four variations of the UMC soft point loading, all measured within .354" to .356" at the case mouth. One early Remington bullet, in a factory cut-away cartridge with the bullet base left whole, showed a measurement of .354". I cannot explain why their production log shows the change to a bigger bullet, and yet all of my rounds measure at the smaller measurement. It may simply be that I never found, or never checked for, any cartridges with larger bullets, but that they do exist. I just don’t know.

What is clear, is that the norm for this cartridge, from beginning to end, was to have basically a 9 mm bullet diameter (.354"-.356" as the spread of most of the specimens).

I found nothing to indicate that any measurement over a maximum of .360" was ever considered, not to say it can’t exist, but simply that I have never seen any documention for one.

I did essentially the same thing on some old USCCo, Western, and WRA .38 ACP rounds I had. But of course, I have no way of knowing just how old they actually are. In any event, my measurements were also around .355". I think is was just another case of someone on the internet not knowing whereof they speak.

Interesting, gentlemen.

As a matter of curiosity, which other of the rimless auto pistol rounds designated “.38” or “.357” actually use 9mm bullets?

Let me rephrase my question in the hope of gaining a response!

I know of a few other auto pistol cartridges which use inch designations: the .38 TJ, .38 Casull (based on necked-down .45 Auto case), and of course the .357 SIG. Do these use .357 or .355 bullets?

Tony - As far as I can tell without pulling bullets (measuring right at the case mouth), all of the.40s necked down to “.38 caliber” use 9 mm (.355") bullets. This includes the three you mentioned plus the .38 JWH. Of course, the 9 mm Dillon is properly named, unlike the .357 SIG.

Thanks John!

Then there’s the .380 which of course is really .355.

Of course - I’d overlooked that one!

Well, there are really many more - 9 mm Nickl, 9 mm Mauser Export, 9 x 21 mm Gyurza (Russian),
9 x 21 “Italian” or “Israeli”, 9 mm Major, and so on, but like the .380 which has the metric name “9 mm Browning Short” they all are probably designated as being “9 mm” cartridges.