My best .338 Win Mag loads pushing 225 gr Noslers are with RL 19 and IMR 4831. Both powders have worked very well, but the Reloader powder gives me slightly higher velocity variation due to big outside temperature changes (70 degrees at the range vs 20 degrees in elk camp - yes I take a chronograph along to camp). I have an OK load with 225 Barnes and IMR 4350, but the Noslers have always shot better for me.