That began in 1935 when Ben Comfort won the 1000 yard Wimbledon trophy at Camp Perry. The win was challenged by other shooters who had long been of impression that the event was for the..30/06 only. However the judges ruled in favor of Comfort, and virtually overnight the .300 H&H became the go-to round for long range competitors and ruled 1000 yard competition for several years.
While I do think the 300 H&H is quite capable of excellent accuracy, a lot of rounds have won the 1000 yard Wimbleton, just due to longevity the 30-06 probably has more wins. This feat of Ben Comfort, well kudo's to him for winning, but I read the number two guy was shooting a M1903 service rifle (irons) and lost out by a V. Ben Comfort's feat is primarily remembered because of one in print gunwriter: Charles Askins. Charles Askins was an in-print troll. He periodically wrote provocative articles , to get angry letters to the editor, which then proved, people were reading his articles. Periodically he would write articles proving the 30-06 was horrible, obsolete, anything it did, other cartridges did better. Charles claimed the 30-06 was obsolete as a target cartridge because Ben Comfort won the Wimbleton with a 300 H&H. He also claimed it was inferior as a hunting cartridge. If Charles were alive today, I wonder if he might have tried getting attention by biting the heads off animals , such as what Ozzie Osbourne did.
I consider it amazing how long the rantings of a troll gun writer have defined this cartridge.
Incidentally, Mo Defino told me someone won the Wimbleton with a 7mm Rem Mag, and according to Mo, that put the Long Range Community behind by years, as it took that long for the long range community to determine on the firing line, that the 7mm Rem Magnum was not the next great thing.
In 1935, yes, Ben Comfort did win the Wimbleton, but the planet did not stop spinning, history did not end, and time has moved on. I suspect the 30-06 was still the most popular long cartridge until the 1970's, because of all the free 30-06 ammunition, all the 30-06 target rifles on the firing line, and that the extra 200-300 feet per second you get with a 300 H&H is not worth the cost or the recoil. From his Team Mates, Larry Moore won the Wimbleton in the early 1960's with a 30-06. If you shoot long range, what you learn, going up in ballistic coefficient adds much more to your score than does a velocity increase. I shot a 30-06 bolt gun, prone, for 1000 yards, and with 200 grain bullets, it kicked. I only got 2700 fps with 200 grain bullets, but it still kicked. It kicked hard enough that it was difficult not to start flinching around the fifth shot. I can't imagine what it would be shooting a 300 H&H prone. I saw very few prone shooters using a 300 Win Magnum. At least prone with a sling, the F Class guys were using it off rests. That round shot well, still too much recoil for a prone rifle. One bud, he built a 30 caliber long range prone rifle around a 30 caliber magnum wildcat, and it was a cannon! I was on the firing line the first time he shot the thing for record. I remember him standing up between relays, blood streaming down his face, because the rear sight had cut him above the eyebrow. The recoil was so stiff that the rear sight went right into his forehead. He was not shooting the thing in the next match. Later I heard, someone got a real deal on that rifle.
I do think the 300 H&H is an excellent round, it has plenty of velocity, it is capable of excellent accuracy, and it feeds and extracts incredibly smoothly. You have to try the thing to feel how easy it is to chamber a round. That highly sloped shoulder contributes to outstanding reliability in feed and extraction. There is a reason funnels are tapered, if you want something to go down the hole, a taper is the better way to go. I am a fan of cartridge taper, those cylindrical Ackley Improved cartridges are finicky in feed, if they get a little off center, they jam easy. Then, when a tapered cartridge relaxes, it relaxes off a diagonal, increasing the clearance between case and chamber. Straight walled cases will drag on extraction, there is an Army study on 5.56 extractor lift, the 5.56 case is one of those Ackley influenced cases, and it drags on extraction, which causes jams.
Both the 7.62 X39 and the recent Chinese 5.8 mm round have more taper than the 5.56 round. The 7.62 X 39 is well known for its function reliability, the 5.8 should be equally as good.