Another chunk of advice. You have a great choice. The 7 mm Rem. Mag. is about as wicked a long range shooter as you can come across for medium game. You can choose a lighter bullet. such as a 130 gr. and see if it'll group. As long as you shy away from any of the bullets that expand rapidly it'll still kill quicklly and there will not be so much tissue damage.

Now if you are of a mind to buy a new rifle, hey why not ? I agree with others that the 280 Rem. is a good round, but it is essentially a 270 Win. and ammo around here is not all that easy to find, and certainly not many different choices. Hand loading the 280 Rem. will give you a ton of good antelope choices. The 25.06 Rem. is also a fine choice for medium game, but again the factory ammo may be a bit difficult to find in many localities and choices are often limited. A 100 - 120 gr. bullet out of this carttridge would be a fine choice.

The suggestion to look at a 7mm/08 Rem. is good. Nice performing short action cartridge and certainly suitable for medium game. Again, might be a bit difficult to find ammo if you are in "Two Dot", but not a bad way to go.