Some chamberings seem akin to magic, the 300 H&H is one of those. While I have never owned one and while I recognize the case design as being just about as bad as it could possibly be, I am, nonetheless, a fan of this circa 1925 cartridge because I know what it can do! There is also the historical perspective to consider. This case was created by necking down the case used for the, circa 1912, 375 H&H. Holland & Holland kept the same, significant, body taper but shortened the body to reduce shoulder angle to about half what was used in the 375, which was already a modest angle. As such, the 300 H&H has an extremely long shoulder. Despite these characteristics, capacity is still significant for a 30-caliber round. Considering the limitations of the propellants then available, capacity was sufficient to allow the 300 H&H to generate all the velocity feasible with any but the largest of 30-caliber chamberings of that era and for long thereafter. Today, when loaded with the best modern propellants, bigger 30-caliber rounds can generate significantly higher velocity but only at the expense of significantly greater recoil, muzzle blast, and barrel heating. Historically, the 300 H&H was once an important cartridge in long-range target shooting. My suspicion is that the taper of the case, combined with the gentle shoulder, allows the propellant the primer does not directly ignite to freely compress. It then can move into and through the case neck very uniformly from one shot to the next. Something must explain why the 300 H&H can deliver world-class accuracy at long-range, and it certainly does. June of 2023, four of us watched Bill Falin first get his zero and then put his last three shots inside 3 inches at 2046 yards using his Custom 300 H&H. Anyone who does not believe he can repeat that should consider that two years earlier he put eight shots in a row into a circle smaller than 6 inches at the same distance. We celebrate the centennial of the 300 H&H as I write this and, after all this time, it remains a fantastic chambering option for both big-game and long-range target shooting. Because it was the fattest case then in common production in the U. S., it along with the 375 H&H, became the basis for a host of factory and wildcat chamberings in every bore size from 25- to 45-caliber. As were myriad wildcat and SAAMI standardized belted–magnum cartridges, this case was derived from the circa 1912, 375 H&H.