Riflenut hit the nail on the head. The .284 Winchester is a unique and excellent round in it's own right, with a rebated head and short fat body. The powder capacity of the case and ballistics are vertually indentical to the .280 Rem. But it is not a .280 Remington. The .284 Win. was designed for the M-88 (lever action) and M-100 (semi-auto) Winchester rifles, from about 1958 to about 1972. This round never became very popular because it was only offerd in this 2 rifles. If it had been offered in the M-70 bolt action, it may have enjoyed more popularity. Now days, when people think of the .284 Win case, they think of "what by .284", like 6mmx.284, .25x.284, or .338x.284. The 6.5mmx.284 is gaining popularity in the 1,000yd shooting clan, becuase of it's excellent ballistics and amazing inherent accuracy.

The .264 Winchester Mag., was toted as the fastest and flattest thing around when it was first introduced back in the mid-late 1950's. But, Winchester had the wrong twist (going off of memory here so I hope I get this right) in the barrel, as it was to fast of a twist and quickly gained a bad reputation as a non-shooter with lighter weight bullets. By the time Winchester corrected this with a slightly slower twist rate in the barrel, the damage had already been done, and the .264 Win Mag. never recovered from it's undeserved bad reputation. Then Remington came out with basically an indentical case just necked up to 7mm (.284), called the 7mm Remington Mag, and the .264 Win. Mag's fate was sealed.