.300 Win. mag.
Load that has worked well for me in more than (1) factory .300 Win. Mag. rifle is 76.0 gr. RL22 Fed. 215 primer in a Winchester brass case (not nickel) using a Nosler 180 gr. Partition. RL22 can vary lot-to-lot and I would start at 72.0 gr. and work up. Some people I know have exceeded 76.0 gr. with certain lots of RL22 but you will only know by trial and error and using it in your particular rifle. My success was tight groups and over 3,000 fps in a 26" barreled Browning A-Bolt & a 24" barreled Remington 700. Both rifles shot under 1 MOA & the Remington was closer to 1/2 MOA consistently. I've also used the same load using Norma MRP when I could find it.