T Inman,

The .250 Savage was introduced just before World War One, and apparently quite a few people necked it down to .22 shortly afterward, sometimes with slight variations, though the first wildcatter to promote it much was Jerry Gebby, who trademarked the name .22 Varminter in 1937. Browning chambered it in factory rifles in 1963, while it was still a wildcat, but it wasn't until 1965 that Remington adopted it a factory round and started making ammunition.

Variations on the .257 Roberts (the 7x57 necked down) also appeared long before Remington made it factory round in 1934. Evidently several wildcatters came up with versions in the 1920s, though Ned Roberts usually gets the historical credit. His cartridge (which he called the .25 Roberts) had a slightly different shoulder angle than Remington's version.

The first person to promote a wildcat usually gets the credit for developing it, even though the basic is a very old one. The 6x57 Mauser, for instance, appeared as a commercial hunting round in the 1890s, but Warren Page (Field & Stream's shooting columnist) "developed" a very similar wildcat round in the mid-20th century. Remington eventually introduced their version as the .244 Remington in the mid-1950s, with a -12 rifling twist which was too slow to always stabilize commercial 100-grain bullets. But the name got changed to the 6mm Remington a few years later when Remington started putting a 1-9 twist in the barrels.

“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck