.458 American, by Frank C. Barnes, I think. a number of months before P.O. Ackley passed away, we were talking about his 3rd book and he asked for my .458 2" data. I sent it, but the book never materialized before he passed.
The data that was in his #2 book, did not come close to the same velocities in my rifle, even though I had, at that time, a quantity of HiVel#2 powder that was used in the data sent to him for that book.
The long throat in my barrel might have been one reason. I got that first .458 2" in the mid 70's & put over 15,000 rounds through it, along with excellent 'grouse' loads using AL8 powder and 230gr. Speer swaged pistol bullets which actually made 3" groups at 100 yards, but shot to the duplex reticle's lower post at 25. Head shot 34 grouse one fall with that rifle while moose & deer hunting. It was a fun gun to shoot a vast variety of loads in.