I have been trying to research this topic for some time without much success. I notice there were some postings about the .30 Remington FBI load made in this forum back in 2008, but those do not really answer my questions.
It is known that the FBI purchased several hundred Remington Model 81 long-recoil semi-automatic rifles in the early 1940’s, and possibly even shortly before that. For reasons unknown, the FBI at that time wished to “duplicate the .351 WSL” (whatever that means) in a .30 Remington load, and requested a “Special Velocity” load in .30 Remington to do that. There is some indication that the FBI load may have used a 160 grain FMJ bullet, but at a reduced muzzle velocity vs. the factory standard .30 Remington load. The Model 81 for FBI service reportedly required a weaker buffer spring to achieve proper functioning using the “Special Velocity” load. Based upon personal experience with the Model 81, this lower velocity is likely to have been below the 1850-1900 ft/sec range required to function the normal .30 Remington Model 81 action using a bullet of this weight.
Can anyone provide greater detail about the specifics of the FBI .30 Remington cartridge, who made it (probably Remington), how it was packaged (I assume it was sold in commercial packaging with some notification that it was a special load), and, if known, why the FBI felt it needed a reduced-power load?