Re: 300 RUM & AA8700
Try Starting at 96-98 gr with the 200gr. and work up from there. 102.5gr of H870 with a 200gr. SMK showed promise in my 300RUM, until I couldnt buy it anymore.
My current favorite load is 92.5gr R25 with the 200gr SMK. Provides consistant .5" groups.
The H870 AA8700 powders are surplus and designed for 20mm gatling guns. The "diry" is carbon that was formulated so the machine guns will not get as hot.
Notice Fiftydrivers posts about wc872, which is basically the same powder and his comments about lower barrel temp.
BTW, these powders seem not to foul as much when loaded to maximum pressures.