Really, the 284 Win. was our first short-fat cartridge. It was also the first in the U.S. with a rebated rim. And one of the first with a 35-degree shoulder. If Winchester had waited until today to release this cartridge, it would be considered cutting edge. In fact, Weatherby recently lengthened the 284 Win. to make its rebated rim 6.5 RPM cartridge.
Oddly, .264” bullets have given the 284 win case its biggest spotlight. Wildcatters have been necking the 284 Win. up and down for decades. The .257 version is fairly popular. Some 6mm versions really scream, but the 6.5mm was so good that a lot of long range target shooters started competing with it. Norma in Sweden took note and, with Winchester sleeping on the job, so to speak, Norma stole the show by commercializing this .264 as the 6.5-284 Norma, not Winchester.
The 6.5-284 Norma became so popular that long range competition shooters wondered what would happen if they necked it up to 7mm. Yup, they “re-created” the 284 Winchester. One Charles Ballard used one to set a National F-Class 1000-yard record by pushing high B.C., 180-grain Berger bullets to 2,900 fps! Now, remember what was said about a long, 175-grain bullet taking up too much powder space in the 284? How was Ballard able to get an even longer, heavier 180-grain bullet to 2,900 fps? For one thing he used a 32-inch barrel. For another, he throated the chamber specifically for 180-grain Bergers seated long in a long, single-shot action. Without the COAL restrictions of a short-action magazine, he could seat his long bullets well out of the powder space, much as one can do with the round chambered in a 30-06-length action.