Flintlock,
While a .243 is capable of shooting, and killing, deer, it has that capability within boundries. Specifically, while many deer can be killed effeciently within 100 yards, I don't consider the .243 to be a 300 yard deer gun. Accordingly, out of the 125 deer that you have killed with your .243, I would safely assume that the average was well under 300 yards, and probably closer in the 100 yard range. Is this correct?
As for shooting a 350 pound bear with an 85 grain non-bonded bullet, although it can be done, there are just too many margins for error, which is probably why even you yourself don't advocate the .243 as a bear gun. Of course I certainly understand that you were probably bringing up that point to say that, if you can kill a bear, then you can easily kill a deer, but even then I would not advocate such an 85 grain bullet in a .243 for deer, especially at longer distances.
Granted, bullet design, weight, and placement are pretty much everything when it comes to killing humanely and effectively. But even then, at longer distances, I believe that you simply need a little bit more punch to drop 'em.
I remember I had my uncle shoot at a beautiful 10 point buck at about 200 yards with a 100 grain Nosler partition out of his Sako. This was about 15 years ago, but the deer was shot in the neck and dropped on the spot. The Partition is an excellent bullet, and the shot placement was equally great. Still, even though he is a great shot, the deer could have moved his neck the second he pulled the trigger, and who knows what would have happened. The margin of error is just a little too high for a .243 at shots close to 300 yards.
Zachary