Re: the best long range varmint caliber
I guess the real question is, how many of the shots are going to be at 1000 yds? If most of the realistic shooting is going to be at shorter range, then a regular old 243 would be a great choice. Without all the case forming, money eating, brass crap work. A nicely built 243 would work excellent out to 7 or 800 even in slightly poor conditions, and on good days, would be a real hoot at 1000 or perhaps farther. A 22-250 will easily handle 600 and give 40% kills on a rodent. Even out of a factory gun. Boyd borrowed and shot my Swift, one time, one shot at 505 or something like that. Dead woodchuck. In poor conditions. Off a tripod. Well, that's not all the gun will do and that was a factory remington with 55 gr bullets. 1:14 twist, that's all I can use. So grab a 6mm-something and head out varmint-in.
At williamsport, last years 6match grp agg winner shot a 6mm and he didn't make it to all the matches. Several others shoot 6's, Chuck Shalansky shot a BR and did great in some terrible conditions that I remember. Not saying you should build one for 1KBR use, but, I wouldn't be afraid to shoot at a critter with one.
Do yourself a favor and stick with the standard case. You'll thank yourself later. (I know from experience. I'm stuck with the one I chose)
If you have something that you disassemble and reassemble enough times, sooner or later, you'll have two!