I am getting used to how this thing works so bear with me. you are looking into varmint class calibers but you did not say what type of varmint you are after. coyote. 25s will do great with the 25-06 as one of my very favorite. 95 gr vmax at 3500 or so and you will pop dogs out to 400 and beyond with ease. if you are looking at rats and rabbits, just stick to the easy to get ammo for 223. lots to load for and lots to buy in the custom lines. not only that but you will save on heat and on barrel life. better then the hotter 224s. I have a 6.5 that is with Craig Boddington right now that will slap the life out of dogs and kill elk when i need it and it was built for under 1,000. marc