Graybeard,
I've never shot anything larger than a rabbit with a hand gun. maybe your right there. But I have shot deer with a lot of different cartridges including, I think 3 with the 243. I don't care for the 243 either as a deer cartridge but, people have been very successful with it. You'll notice I also said: "suitable bullet and good shot placement. I saw a guy shoot a good buck in the butt with some Federal factory load, 180gr, from a 30-06 that did not exit. While the bullet was probally suitable, the shot placement stunk!
I also recovered one 117gr bullet from a 25-06 out of a deer that had gone in, struck a bone and vered off course up the spine. The spine was shattered for a good ways and the bullet was lodged several inches below the head, in the spine. I suspect that had the same shot been taken with one of my 6.5's, the bullet would have cleared. I strongly believe that the best bullet's for hunting what we call big game in any caliber, are the mid to heavy bullet's and would not concider less than 100grs in 24 cal. Anyway, that is the extent of my recovered bullet's in deer. One recovered bullet in a bear was a 140gr Sierra from a 7mm Rem mag, if you could call what was recovered a bullet. Choice of bullet was bad but the placement was good. Head on the bullet hit the bear in the center of the chest, I'm not sure any bullet I'd care to shoot would penetrate the entire length of a bear.
Have also shot a number of elk and never recovered a bullet. Again, for me good shot placement is the route of least resistence to the vital's. If someone in fact want's to shoot light for caliber bullet's and see how much mass they can get thru and still kill an animal, complete penetration may well become suspect. Again I'm also talking about only rifle cartridges, I know little of handguns in big game hunting. I have heard many stories of light weight, lightly constructed bullet's doing incredable thing's. For the most part I believe they are stories to justify the use of to light a bullet at high velocity and usually in to small a cal. We see where different bullet manufacture's are indeed offering better constructed bullet's in these cal's, ie: the 22 cal Nosler partition. Given enough velocity I'm sure they penetrate beyond their size. But velocity and energy fall off rapidly putting them into the short range show off cataglory to me.
It would be hard to stop a well constructed, suitable bullet, from a legal cartridge with good shot placement from exiting. Of course, all exit wound's are not equal!