See my earlier post, No. 31, dating to Nov. 17, 2009 concerning the 130 gr. full metal jacekt bullet.
Here's an excerpt:

"The standard M41 ball is loaded to standard .38 Special pressures of 16,000 psi maximum and develops 950 fps (plus or minus 25 fps) from a 6" solid test barrel.
The American Rifleman chronographed the M41 cartridge at 720 to 770 fps. This velocity is about the minimum at which a jacketed bullet can be expelled from a revolver.

PGU-12/B has a deep-seated bullet and heavy crimp. The headstamp includes the telltale +P marking. This cartridge gets 1,125 fps (plus or minus 25 fps) from a 6" solid test barrel. Maximum allowable pressure is 20,000 psi, which certainly qualifies it as +P.
The American Rifleman staff chronographed these same rounds from a 4" barrel at 950 to 980 fps."

I was honorably discharged in January 1979. I never saw PGU rounds. Our duty-issue ammo was the M41: 130gr. at 750 fps. The Air Force was experimenting with the PGU, and probably issued it to others deemed more needy (SAC, bodyguards, Air Force One guards, etc.) but we never saw it in Denver or Panama.