The Alaskan, the FBI load was a 38 Special loaded to +P velocity using a 158 grain plain lead bullet usually described as a "semi-wadcutter hollow point".
A semi-wadcutter is sometimes described as a Keith-style bullet, after Elmer Keith. (I don't know if he invented the form, but he was very much associated with it.) It is a slightly sub-caliber truncated cone on top of a full-caliber cylindrical base. You can probably Google up a picture of it, or of a lead semi-wadcutter hollow point (which abbreviates to LSWCHP) pretty easily.
The factory FBI loads had "swaged" lead bullets, which means that a piece of soft lead of the correct weight was pressed into a die to produce the desired shape. Swaged bullets are quite soft, generally softer than cast bullets, which aids the expansion of a hollow point. (As I understand it, most plain lead bullets by major manufacturers are swaged, because the method is well suited to mass production.)
I believe the FBI load was also sometimes known as the Chicago load, or the Metro load (after Metro Miami?), because these police forces were also early adopters of it. I don't know if the FBI developed it in-house, or if it was done by one of the ammunition manufacturers, or a handloader. I know a company called Super Vel (founded by a man named Lee Jurras) began marketing hollowpoint pistol ammunition in the early 1970s, but I don't know if the FBI load was one of their products.
Thirty-five years or forty years ago, this was one of the first hollowpoint loads to be recognized as effective and reliable, and to achieve wide acceptance in law enforcement. With crime rising since the mid-1960s, many law enforcement agencies had come to recognize that the traditional 38 Special standard-velocity round-nose lead bullet often lacked effectiveness, even with a solid hit. Many agencies did not wish to spend the money for new guns, and many policemen disliked the heavy recoil, flash, and blast of 357 Magnum, so the FBI load presented a very attractive solution.
In this thread, posters have suggested that major manufacturers have reduced the muzzle velocity of their 38 Special +P ammunition. This might be unusually important for their +P 158 gr. LSWCHP loads, since it is unusually heavy for a 38 caliber (actually .357 inch or 9mm) hollowpoint and may have been near the lower limit of the velocity required for effective expansion in the first place. I have no chronograph and do not shoot enough 38 Special ammunition to have an opinion.
I hope this answers your question, and I apologize if it is more than you wanted to know.
