Since you have the GMXs, give 'em a whirl.
But, I'd be more worried about lead poisoning from # 7 1/2 or # 8 shot dove/quail loads, which have helped stock my freezer for decades.
My typical deer (and we eat a lot of venison) is taken with a Sierra Pro-Hunter through the chest. We skin and quarter, saving also the backstraps and tenderloins. Rib cage gets left to the coyotes/bobcats/pigs/vultures anyway, along with practically any potential lead contaminants. I've never given lead a second thought!
If your rifle likes brand x of 4350, I'd start there. My 24 inch .280 prefers RL-22 (should be almost identical to Norma MRP) behind the 140 gr. Sierras, with RP brass and Fed 215 primers. Muzzle velocities with my rifle, and a carefully-worked-up-to charge, kiss 3000 fps with consistent accuracy. YMMV.
