How the 243Win. stacks up? Not too well
The following from Chuck Hawks site ref. killing power of various cartridges used for big game hunting.
Website Link: http://www.chuckhawks.com/rifle_killing_power_list.htm

"The list that follows is intended to suggest the relative killing power of various big game hunting cartridges and loads at 100 yards (or meters, if you prefer) when those cartridges are used appropriately. (Cartridge, bullet weight in grains, muzzle velocity in feet per second - killing power number at 100 yards.)"

.223 WSSM (64 grain at 3600 fps) - 10.1

.243 Winchester (100 grain at 2960 fps) - 18.1

.243 WSSM (100 grain at 3100 fps) - 20.0

.25-06 Remington (120 grain at 2990 fps) - 26.5

6.5x55 SE (140 grain at 2700 fps) - 30.7

6.5mm Remington Magnum (120 grain at 3210 fps) - 30.2

.270 Winchester (130 grain at 3150 fps) - 35.0

.270 Winchester (150 grain at 2850 fps) - 37.4

.270 WSM (140 grain at 3125 fps) - 40.1

7mm-08 Remington (140 grain at 2860 fps) - 33.6

.280 Remington (140 grain at 3000 fps) - 37.1

7mm Remington Magnum (150 grain at 3110 fps) - 44.8

.30-30 Winchester (150 grain at 2390 fps) - 22.8
.30-30 Winchester (170 grain at 2200 fps) - 25.4

.300 Savage (150 grain at 2630 fps) - 30.0

.308 Winchester (150 grain at 2820 fps) - 34.7
.308 Winchester (180 grain at 2620 fps) - 46.2

.30-06 Springfield (150 grain at 2920 fps) - 37.3
.30-06 Springfield (180 grain at 2700 fps) - 49.2

.300 WSM (180 grain at 2960 fps) - 59.5

.300 Winchester Magnum (180 grain at 2960 fps) - 59.5

.300 Weatherby Magnum (180 grain at 3240 fps) - 72.8

7.62x39 Soviet (123 grain at 2365 fps) - 15.7

.303 British (180 grain at 2460 fps) - 40.1

8x57 JS Mauser (195 grain at 2550 fps) - 52.0

.338 Winchester Magnum (250 grain at 2650 fps) - 94.8

.35 Whelen (200 at 2675 fps) - 56.4

.350 Remington Magnum (200 grain at 2770 fps) - 60.9

.375 H&H Magnum (270 grain at 2690 fps) - 106.2

.416 Remington Magnum (400 grain at 2400 fps) - 188.4

.44 Remington Magnum (Rifle) (240 grain at 1760 fps) - 26.4

.444 Marlin (265 grain at 2325 fps) - 63.4

.45-70 Government (300 grain at 1810 fps) - 50.1
.45-70 Government (405 grain at 1330 fps) - 55.0

.450 Marlin (350 grain at 2100 fps) - 88.9

.458 Winchester Magnum (500 grain at 2090 fps) - 217.3

.....................................
Nope, not too well at all!!!