Memories of handloading
Just came across the first reloading manual I ever used, back when I was 16-17 and loading with a Lyman tong tool (don't think they make them anymore, but I still have mine). It's P O Ackley's Pocket Manual for Shooters and Reloaders, 1964 edition.
Quite a look back, to the days when the .22-250 and .25-06 were wildcats, and the .223 so new that he doesn't have a table for it, just a note that Remington's chief designer say 22 graints of 4198 is close to max with 50-53 gr. bullets.
Tons of older wildcats that you'll probably not see today, most developed in the 1920s and 1930s when small bore centerfires had few factory cartridges. .22 K Hornet, .218 Bee, Mashburn Bee, .219 Zipper and Zipper Improved.
For you young'uns, the Improved cartridges stem from the 19th century practice of designing cartridges with lots of body taper, long shoulders, and long necks. You improved them by designing a chamber with little body taper, a steeper shoulder and shorter neck. When you fired a factory cartridge it expanded to fill the chamber (with some losses when the brass couldn't take it). Since the newformed cartridge had more internal capacity, you could then handload it to greater power. It worked a lot better with rimmed cartridges, since the rim held them in place. With rimless it could get dicey, since there was only modest contact between shoulder of the factory cartridge and shoulder of the chamber.