Re: long range calibers
for hunting out to 1k, you're probably going to need something in the 30 cal range for energy.
as far as punching paper, truth be known, just about anything will work. its easier than most people think, and as stated above, the new record was set with a 6br. although i think 223 is a tad light, i've shot beside a guy with 243 and watched him run right with me and my 300rum.
half of it is about working out a good LR load than will remain stable and subsonic out that far. just about any gun can do it, you have have to find a good bullet/load combo.
most 1k shooters will tell you thought its all about wind out there. put someone beside me that can read it good with any gun, and they'll kick me and my 300rum's ass all day long.
caliber is more of a preference thing, and anything 243 and up will do it fine. for hunting though, stick on the larger size to keep energy levels up.
If it were easy, I wouldn't be doing it.