Those looking for the ultimate whitetail cartridge need look no further, 25 WSSM has arrived.
Yes, cause as we all now know the 25-06 is now an inferior round.


Too bad he asked for a varmint cartridge.
If you are wanting a cartridge for primarily varmints but still actually plan on using it for the occasional deer the .243 Win would be about your best bet. Factory ammo can be bought with bullets weighing as little as 50 or 55 grains for the varmints and doing about 3800 fps or so out of the barrel and then step up to the 85 to 100 grain bullets leaving the gun between 3000 and 3300 fps. for deer.
Now if you already have a deer rifle then I would definetly go with a 22 centerfire. My choice would be a .223 simply because they are much cheaper to shoot.