300 Win Mag or 300 Rem Ultra Mag, either cartridge is not a varmint round persay and can be a bit hard on the shoulder after a day of shooting. Forget the accelerators. You might be lucky to hit the broadside of a barn with them if you are close enough. If you are looking for a varmint rife that you can use as a deer sized game rifle in a pinch then consider the 243 Win or the 6mm Rem both are very capable of taking deer and are accurate, mild recoiling cartirdges. Moving up you have the 25-06 Rem and the 257 Roberts then there are the 260 Rem and the 6.5X55. I had a buddy that used to pop prarie dogs all day with the same Win Model 70 in 270 Win that he hunted with. The 7mm-08 Rem would also be a good cartridge as would a 308 Win. Lots of choices out there besides a 22-250 Rem or a 300 Win Mag that would probably better serve your needs.