From what I gather, this was one of the wildcat forefathers ideas, an offering from PO Ackley, of Ackley improved fame. Simply put he used the 221 Fireball case and necked it down to 17 cal. He called it the 17/21 and it could push a 20 gr bullet to just over 4200 fps, this all happened in 1962, thanks to Vern O'Brien, a Vegas gunsmith who took the idea and chambered it in rifles.
In 2007 Remington looked at the old Wildcat 17/21 and made a few changes to neck angle etc and called it the Remington Fireball, the cartridge we know today.
Today bullets are available in weights from 20 gr to 30 gr with the 30 gr Berger bullet being capable of 3500fps + and the 20 gr AccuTip realizing 4200 fps +
All this comes with only 16 - 20 gr of propellent being burnt, which was supposed to help reduce fouling, but reports are more to the lament of rapid fouling of the barrel.
The calibre is described as accurate, flat shooting and mild in recoil, suitable for medium range varminting. I would imagine that a 20 gr bullet does not come with much kinetic energy, even at 4000 fps ? Comments required here.
I do not know of this calibres application over and above shits and giggles in the RSA, perhaps Dassie and crows, I do not think (based on .204 Ruger results) that it would really be suitable for African vermin, like Monkeys, Jackal, if ethics are a consideration.
The Fireball it would appear lost popularity to the the 17 Remington, which just had an overall "better" performance and reduced barrel fouling characteristics.