[Unclenick]

The SAAMI maximum length of a 380 is 0.984" and the minimum for 9mm is 1.00". Those are close enough that I would expect full-length 380 FMJs to function in a 9mm magazine. If it proves to be a problem. For shorter hollow point loads, it may well be an issue.

I still wonder, since the angle of the reduced-size Browning mag will still be right, if one might possibly use a 3D printer to extend the bottom and fill in the back and sides of it. Be some trimming and fiddling work, but it might be possible to work out an adapter for one that the front toe has been trimmed off of. I've never seen one up close, so I am just speculating here.

The barrel Zukiphile found claims to be a match barrel, but I can't make out the usual dog nut you see on those. That's good because that means it can, indeed, be shortened and recrowned. But having someone with a lathe add the dog nut to match the shorter length will make it easier to fit a solid bushing closely if shooting precision is of interest.