Re: anyone used 210 smk on a 300 rum ??
What other powders are available to you? If you can get a slower powder even the 50 cal VV powders will work well. Reloader 25/ IMR7828, Accurate Arms *700, Vectan Tu8000and VVN170 or VV20N29 would all be better than H4831
Use the slowest powder you can get hold off.