Hey Devil Dog,
I have a box of the 200gr 35cal Barnes "X" bullets made for a rifle cartridge. My initial, unsubstantiated concern would be for the length of the bullets. Solid copper bullets are longer than the same weight lead core bullets. Twist rates usually refer to the weight of a bullet, but really indicate optimal bullet length. The length of the Barnes bullet's body is nearly 1/8" longer than that of a 200gr Hornady Interlock SP. It may work fine, but also consider the optimal velocity ranges for bullet expansion.
Good luck out their in So Cal. Going to 29 Stumps?
Thanks, Dinny