One of my late great outfitter-gunsmith friends never could get the 243 to shoot accurately enough for him.
I don't believe the powder explanation. Other well known cartridges would show the same problem, and they don't, do they?
I think the 243 has always been a great antelope/deer cartridge, and nothing today changes my mind about that.
I've always been troubled by duo purpose cartridges. They're sold on versatility but give something up at either end to achieve it. We want our cake and eat it too. Also, there is a tendancy to use the 243 on bigger game than it is designed for. This would lead to 'erratic' results.
Noahzark leade explanation sounds good, but the trouble is there are the same issues for many rounds normally well regarded- like the 7 mag for instance. One year Speer threw up their hands in despair over that- unable to obtain the published velocities within SAAMI spec of other sources. They wondered if the chamber throats of some rifles had worn or were long.
But for the 243 to be called 'erratic' would mean something there not present in other cartridges. What is it?
I think it's the duo purpose role and using the wrong bullet weight. And on that, individual rifles do seem to vary. The 444 Marlin is not supposed to be able to stablize the larger 44 cal bullets, but in some guns does just fine.
I've always wanted a 243 (but then, the list of cartridges I haven't wanted is kinda small) I wouldn't let one blurb in a gun book change my mind if I wanted one. There is always the real possibilty the rifle would tend to shoot the lighter or the heavier bullets best, but not both.
munk