You can't beat the 223 for all around varmint hunting. It will reach to 300-400 yards on a small varmint and is VERY cheap to shoot.
Plus, full metal jackets and soft points are available for small game hunting...OR reduced loads.
204 Ruger is WAY WAY too powerful for small game hunting at any range because ALL you can buy for it now is ballistic tips or hollowpoints, both designed for maximum energy transfer and damage on varmints.
17HMR is generally nasty on small game unless you use the new 20 grain loads (Hornady or CCI). However, I wouldn't consider it a good all around varmint rifle. I use mine for strictly small, small varmints (Starlings, field mice). It is great for that purpose too!! It will however kill larger game but you will have to put the bullet in the right area. A gut shot groundhog will run away every time.
22-250 is a great long range varmint caliber. It will produce about 300-400fps faster than the 223 but with more expense in powder and money and barrels and kick. The only reason I would buy a 22-250 would be if I wanted a long range varmint gun in 22 caliber. I already have a long range varmint caliber however, a 25-06. It will do all the 22-250 will do and much much more at longer ranges. If you are even good enough to extend the 250's range to it's max it would still be a hard choice to make over other calibers that will do the same.
Some reasons to recommend the 223 are:
-Cheap
-Effective out to 400 yards on medium varmints (groundhog)
-Fast with 30 grain bullets (4000+ fps)
-Up to 100 grain bullets can be used (Barnes I believe make these)
-Small powder consumption
-No kick for the view of bullet impact
-Inherently accurate
-EVERYBODY makes 223 so availability is there
-Small game up to deer if you wish (64 grain PowerPoint from Win)
If you want another gun for better range on varmint go for something like a 243 or 25-06. They will be much better than a 22 cal centerfire for varmints at long range. (500+ yards)
