I haven't had a truly "odd" thought stream in a while. And then, one struck.
.38 S&W. 9mm Makarov. Has anyone ever really looked at how close these are?
1 - With a .002" swaging, you should be able to load ~95gr Makarov bullets in .38 S&W cases, and probably get close to the listed 1000fps ballistics (if you can get 800fps from a 158gr, you ought to be well within pressures with a 200fps rise on a bullet less than 2/3 the weight). If I had a ballistics simulation program I could figure what .361"@95gr FMJ into 14Kpsi ends up being, but I don't.
2 - With relatively little work, one could modify a makarov-based platform into a .38 S&W single shot and possibly still get reasonable accuracy of it. The .38 case is only 0.060 longer roughly, and the rim could be accounted for by filing the end of the chamber down... you may have the bullet stuck into the rifling but you're 0.002" undersized soft lead.
3 - With even less work, and some crossed fingers, it seems to me that one could, given a suitably strong pistol, shoot 9mm Mak out of a .38 S&W revolver. I AM IN NO WAY, SHAPE, OR FORM ADVOCATING ANYONE ATTEMPT THIS. .38 S&W is 14,000psi, Mak is 23,000PSI, halfway between .38sp +P and .357 Magnum. I'm just looking at the numbers here... if you stuck a .015" thickness C-clip into the extractor rim of a mak cartridge, you have a reasonable, though .002" oversized, approximation of the size of the .38 S&W.
You will very probably damage the gun beyond repair, but that's handy to know if you're stuck in the middle of nowhere during zombie apocalypse, and you have everything and the kitchen sink with you as far as "common" calibers, but someone in your party has Grandad's old Enfield tanker and no ammo. One zombie, two zombie, three zombie, four, *ping* there goes the top latch, gun's thoroughly toast but you're +4 better in the odds bank, better some help than none right?
Ramble ramble ramble...