Hi VigII, the best all around varmint caliber is the .223. I have several of them, one a custom Rem. 700/ .223 Ackley Improved, one in a custom AR15 varmint rig, and one in a light Stainless Rem 700 rig. The .223 is adequate out to 2-300 yds on coyotes, ground hogs and Prarie Dogs. The .223 is cheap to buy good ammo for, or if you reload it cheap to reload..it's not terribly fussy to get it to be quite accurate.
The problem i have with the .17 is that it is prone to coppering up the barrel.. and it is a royal pain to clean a .17 caliber barrel..
If I had to choose one cartridge for most varmints, it would be the .223.
Just to give you a run down, I've shot or currently shoot, .22 Hornet, .218BEE, .221Fireball, .222, .223, .223 Ackely Improved, 22-250, .243 win. .243 Ackley Improved, .260 Rem Improved, .257 Roberts.
I'm pretty amazed that the PRB coal will spontaneously combust.. Anthracite coal is inert, in fact is sometimes is pretty hard to ignite even with a torch!!
Charlie I sent you a PM.