I don't know about the .220 Swift, but I don't think there is a hyena that my 243win wouldn't kill reasonably quickly (or instantly).
243 was designed for American hunters, to combine varmint hunting with lighter bullet, and white tail hunting with heavier bullet in the same rifle.
One rifle for everything, was the idea, for common Joe.
Therefore, hunting anything above white tail size with 243, is pushing.
Yes, under the premises that every bullet kills, you can probably have a lucky shot with premium bullet at something like oryx.
And it wont make the daily news. It has been done, I am certain
On the other hand, marginal shot on large antelope will most likely lead to tracking and possible loss of animal.
Hunters are generally happy when they get an animal.
But that is nothing, because in that moment, when animal is down, (especially DG animal) you should take a look at trackers faces.
They are all smiles,
That is pure, true happiness.
And there is a reason for this.
Tracking wounded animal, DG or not, adds stress, uncertainty and bad mood to all team, especially if tracking is prolonged for next day.
Dg animal tracking, will ad a level of danger and risk to entire team.
Personally, I dont need that on safari.
Luckily, these days in modern Africa, there are laws about hunting and minimum calibers.
So, even with the best intentions to multipurpose 243 for everything, they will not allow you to hunt just about anything with 243:
For example, for Namibia, here are caliber / energy requirements.
Minimum Caliber and Energy Tiers
Small Game (Springbok, Duiker, Steenbok): Minimum .243 caliber with at least 1,350 Joules of muzzle energy.
Medium/Large Game (Kudu, Gemsbok/Oryx, Eland, Hartebeest, Wildebeest): Minimum .270 caliber (or 7mm) with at least 2,700 Joules of muzzle energy.
Dangerous Game (Elephant, Rhino, Buffalo, Lion): Minimum .375 caliber with at least 5,400 Joules of muzzle energy.