Gut shots with the 243 will do a lot of Damage and if the liver is effective they will often just waver a bit and lay down and die. There is no excuse of course for going that route but gut shoit animals that I have seen were not effected much by caliber size. Years ago when the old black powder cartridge like the 44-40 were common, folks would juust pop elk in the mid section and wait a few minutes for them to lay down and die. Unethical as hell but effective. Bigger calibers can make a difference if big bones or bad angles are in play but thats up to the hunter. Good shot with good bullets from most any midium size cartridge will do the job. Its just fine to make 30-06 your minimum camp rifle, thats your right and a good policy. Fior use who have had great success with both smaller and larger cartridges will continue to do so as well. I use the 30-06 mostly now but wouldn't hesitate to step down to the 308 size cases and the 270&280. I would draw my own line at the 264 bullet. This even though MANY elk have been taken with the 25-06 as well. Not for me. ANd certainly, no 243's.