Did you know you can shoot regular .280 Remington factory ammo in a .280 AI? They shoot fine, and the fired cases come out of theejection portwith the steeper shoulder angle. You could do this until you got a quantity of brass accumulated. Then get into the AI reloading - which will give you about the same performance as a 7 Rem Mag.

Or you could just get a 7 Rem Mag. Huge selection of factory ammo. And even load it down to .280 Remington performance if the recoil was a bit much in gun so light.