This comment responds to one of the questions above. From what I've been able to deduce, the statement that 95% of hunters cannot hit an elk in the vitals at 450 yards would be entirely true. I would be willing to bet that I could NOT put a first shot into a vital sized target at 450 yards, even if some other shooter got my rifle sighted in for 450 yards. I have read that seasoned guides say things like 80% of their hunters can hit vitals at 100 yards; 30% can hit vitals at 200 yards; maybe 10% can hit vitals at 300 yards. Actually, it might be even worse than this. Any guides out there willing to make any generalizations on the marksmanship of your clients?
My guess is that many hunters only shoot their guns at game animals during the hunting season -- no pre-season shooting range work. Of those who shoot their guns at paper, how many of these shoot more than enought to deem their rifles sighted in? How many shoot a box of cartridges a year? How many shoot five boxes of cartridges a year? How many shoot at paper located more than 100 yards away?
I live in a suburb north of Dallas. I know of two shooting ranges. Both are about 50 miles away. I don't go there to shoot very often. I'll go out probably in June or July to see how my .30-06 rifles are shooting. If they are sighted in, I probably won't make the 50 mile drive again until late September to see if they are still shooting where they are supposed to and to confirm the rifles are still OK. Sure, low probability of any mechanical difficulties, but I'ld rather know a couple or three weeks before elk season rather than when sighting in two days before the season opens out in Colorado.
I'm not a trophy hunter. My usual shooting takes places at moderate distances. I took my 2009 elk at well under 100 yards, maybe at about 50 yards. I've shot deer at 15 yards, 25 yards, 140 yards. I shot a pronghorn antelope at 240 yards from a prone shooting position. Under these circumstances I do not feel the need to practice shooting at extended ranges. If the animal is too far away, I don't shoot, I try to move closer, or I wait to encounter another animal. When you aren't hunting for trophies you can afford to pass on an out-of-range animal.
I think a .243 ought to be used for deer and pronghorn antelope and varmints. If you are going after elk or bear you probably are wise to use a bigger gun. But that is only my opinion. Also, if all you have is a .243, that might change the picture a bit. For example, when I'm shooting a cow elk at 40 yards in October, probably a .243 would work . . . but I've got a couple of .30-06 rifles so I'll use one of those instead. I'll take my .243 Winchester featherweight and/or my .25-06 -- both of which I love dearly -- when I'm out pronghorn hunting or deer hunting and then leave the .30-06 at home.