Some years ago, I heard an "Urban Legend" that back in the 1970s, some gunsmiths had converted Model 39s from 9mm to .38 Super. Anyone else ever hear of this? It seems doubtful because the OAL of the 'Super is more than the 9mm, and unless the bullet is seated deeper, it will not fit in the magazine. I'll tell you this - if it is true, I WANT ONE!

The SAAMI Spec on a 9 m.m. X 19.15 m.m. (Luger/Parabellum) is 1.100" - 1.169" OAL.
The .38 Super per SAAMI Spec is 1.220" - 1.280" OAL.
That will not fit in a 9 m.m. magazine.
Now a 9 m.m. X 23 m.m. SAAMI Spec for OAL is 1.150" - 1.300", so,
depending where you seat the bullet point it is capable of working.
Regards,
BM1

In George Nonte's "Pistolsmithing", Chapter 26, he discusses converting a Model 39 to 38 Super. He explains that this limits cartridge OAL to 1.150", which was to be achieved by using 90-100 gr HPs.

Thanks for the info guys. At least I know the rumor is true.

This conversion was also written up in the March '71 SHOOTING TIMES and the 8th edition of HANDLOADER'S DIGEST. Seventrees was listed as a source for the conversion.

Years later, an easier conversion was the ill-fated .356 TSW.

Good shooting.

At the time I had just sold a .38 super to get the double action of the model 39-2. I liked the .38 super and when I saw the article about the conversion I cut it out and kept it.
If I recall... the chamber has to be reamed deeper for the longer case of the .38 super and the bullet has to seated deeper to get OAL to match the 9mm.
I may still have the article at work... I'll look Monday.

I found the article.

Combat Handguns Oct 1982
Let me know if you need more info.

Basically you ream the chamber for depth and the fact that 9mm is a tapered case. Then you need to seat the bullet deeper for OAL

Gotta wonder if this is really worth the effort. In some of the +P+ loadings, the 9mm is right up there with the super. Super brass is hard to come by and $$$.

and +P+ 9mm ammo has got to be brutal for an alloy framed pistol if it is a regular diet. Now in a 3906, that would be a decent conversion.

By the time you use a light bullet and deep seat it to get correct OAL, have you really gained anything?

Sorta similar. I had wondered if a .40 could be converted back up to
10mm? Same bullet diameter. Seemed like the chamber could be reamed, maybe the ejection port milled or rear ramped so brass would clear and not "dent" (did that with a Colt .45 Commanding Officer's model) Ideas?

I read those articles years ago and still have the Nonte/Ezell book, "Combat Handguns". Using the same bullet weight, at the same pressure, at the same overall 9MM length, rechambering a 9MM barrel to .38 super gains Nothing, unless you want to shoot real light bullets for the caliber. In fact, .38 Super, even at standard pressures, will bulge the cases in such a chamber. I had a Super barrel that would also chamber 9X23 Win. perfectly and, of course, 9X19MM. Factory Super loads never blew a case head, but did show significant bulging. If you can load out to standard Super lengths, yes, the Super can out perform the 9, otherwise, not so much...ymmv

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I think ISP was running that round out their 439s and 5904s. Supposedly they held up very well. Dale

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