Malamute said: Softpoint pistol ammo was around because many guns didn't feed the hollowpoints tried. Its generally felt to be deeper penetrating and slower opening than hollowpoints. Old gun catalogs from the 1940s showed softpoint 9mm and other loads. Keith commented on them, wondering why they had been dropped, and stating they improved the performance of most auto pistol calibers they were available in.
When the Illinois State Police adopted the S&W Model 39 9mm automatic pistol back in the 1970's, they used a soft-nosed 9mm round called the "Power Point" and made by Winchester, IIRC. From what I have read, performance was really no different from hardball FMJ. I think it takes a lot more than 9mm levels of energy, and possibly more than 357 Magnum levels of energy, to get soft-nosed bullets to expand, unless you pre-cut the jacket or something.
I would bet those pre-WWII hollow-points had tiny hollows, like rifle ammunition. I have a Mexican CBC 44 Auto Mag HP cartridge, and the hollow is tiny, not like today's pistol ammo. Also, while I have seen lots of old soft-nosed pistol ammo in 25 ACP, 32 ACP, 380 ACP, 9mm Para, and even 35 S&W, I have never seen a hollow point of the same vintage. (Of course, I may have automatically assumed any such round was a reload.) But it must be scarce stuff.
Those mushroom bullets might have had round-nose full metal jackets that were not filled to the tip with lead, but instead had a hollow space under the nose. I have no source for that, and cannot recall why I think so. Maybe one of the old Barnes "Cartridges of the World" books?