Here is the story of +P 38 special in the Air Force as I remember it. There have been other threads on the forum which have seen some of this information.
1. M-1943 Ball was the standard stock listed carry ammunition for Air Police and others from post WW2 into the mid 1970s. It was a 130 grain bullet going about 750fps. This was not the spicy stuff you see loaded commercially now with the 130 FMJ. I think it was developed for the aluminum frame and cylinder models first seen in the 1950s. I believe the Navy used this ammo also in addition to 38 tracer, and I am not sure what the Army did.
2. In the beginning (1947) the new USAF used the M-2 30 caliber carbine and the M-1911A1. This changed in the late 1950s early 1960s when Curtis LeMay took over as Chief of Staff, he liked revolvers. The main complaint from the field being the aircrews had a hell of a time qualifying with the M-1911A1. It was heavy, the sights sucked and it had that single action semi-auto safety/training issue that came up again the the 1970s part of the push for a double action semi-auto. As some of you may recall, the USAF was the first service to jump on the AR-15 wagon in order to dump the M-1 Carbine.
3. We qualified with mostly wadcutter ammuntition, the standard course of fire being 50 rounds. There was an extra course of fire after the standard run for Air Police/Combat shooters. Range guns were fired a lot and cleaned after shooting by folks who for the most part had little patience with solvents and brushes.
4. At some time around 1970 or so, some Navy guy doing some shooting off the end of a ship somewhere managed to fire 5 rounds of the M-1943 ball from his revolver with none exiting the barrel. I saw pictures of this. The first round made it to the end and poked its little nose out, the next ones went bang and lined up behind it. Number 5 lodged partway in the forcing cone locking up the cylinder rotation. So we had some old ammo around not going bang too well, and the lethality issues from RVN. Can you imagine being on a B-52 downed somewhere in Alaska with a 38 and that ammunition? The joke in survival school was it's only practical use was suicide.
5. The solution found for the issue after some testing was the PGU-12 round which was the same bullet seated deeper with an extra grain of powder. We now had a +P load. I want to say it bumped the 130 grain FMJ up into the 900FPS level out of a 4" barrel. It became the new carry and qualification ammunition after stocks of the old stuff and wadcutter was fired off.
6. Old range guns shot thousands of times with target loads now getting a diet of +P. What I heard was they were seeing parts breakage and timing issues. This helped set the stage for what developed later with the Joint Service Small Arms Program (JSSAP) and the request for proposal that went out for a 9mm handgun for DOD. Revolvers were breaking down and the 45s were on their second or third re-build; time for new stuff.
Sorry this took so long. I invite corrections and comments. I was a player from 1968 to 1991 with some breaks here and there.