My disdain for the 243 is from the deer culling days when the govt shooters went from the 303 as imports became more available and the 222 and the 243 became the rifles to use and they were successfull EXCEPT on the big west coast reds and wapiti in the winter where the wet hides (and they were very often wet in this high rainfall area) and when the animals were wallowing, were causesing penetration problems so there were wounding and loss stories. It seemed that if the shot was quartering away the bullet might travel in with the lay of the hair but for a quartering on and even sometimes a square on shot the bullet would sometimes blow up on the wet hide leaving a wound but no penetration sufficient to kill.
Many of the shooters went to the BSA in 7x57 or winchesters in 270 and 30-06 and the problems stopped happening.
I readily acknowledge that it may have been bullet problem (weight and or construction) but once those cartridge predudices are internalised through that type of evidence they are not easily let go of and I for one have not done so and for me deer cartridges start at the 6.5 x55/57 through the 7x57 and on up to the various 30 cals.
So while in dry conditions and with suitable bullets the 243 may well be a usefull cartridge in many areas, for me it will always be too small for deer and too big for rabbits making it useless to all intents and purposes although it may be ok to train youngsters at the range so they can graduate to a propper rifle for hunting