9.3mm bullets have a diameter of .366". Until now, Hornady has not made a .366" bullet, although Barnes, Nosler, Speer, Swift, and Woodleigh (among others) do. Presumably the new Hornady bullet will be offered to reloaders in due course.
The 9.3x74R uses a long, tapered, rimmed case with a small shoulder set at a slight 5 degree 29 second angle. It makes you wonder why the designer bothered with the shoulder at all. (The answer is that the 9.3x74R's black powder predecessor, the 9.3x72R, had a straight-taper case and the smokeless powder 9.3x74R was designed not to fit in black powder rifles for reasons of safety.) The cartridge dimensions are as follows: .5116" rim diameter, .4685" base diameter, .4094" shoulder diameter, and .3905" neck diameter. The case length is 2.941" and the cartridge overall length is 3.665".
Traditional 9.3x74R ballistics call for a 286 grain bullet at a muzzle velocity of 2360 fps with 3538 ft. lbs. of muzzle energy. That is the load for which most doubles and drillings are regulated. It puts the 9.3x74 a little above the .35 Whelen and about equal to the .375 H&H Flanged Magnum in power. The cartridge has been used on large and dangerous game all over the world, particularly Africa, where it has been popular with European hunters for decades. For more on the 9.3x74R, see the Guns and Shooting Online article on the Rifle Cartridge Page.