Hatcher talks of a National Match load comparing two similar burn rate powders that I infer were IMR 1185 and IMR 1186, both now discontinued types. The IMR 1185 grains were 0.032"×0.084" (Diameter×Length). IMR 1186 grains were 0.029"×0.042". Both 1185 and 1186 had 7% DNT deterrent coatings. Hatcher found his arsenal loading equipment could dispense the shorter, narrower IMR 1186 grains to ±0.3 grains, but could only dispense the coarser IMR 1185 to ±0.75 grains. Nonetheless, the sloppy IMR 1185 charge weight spread produced consistently tighter groups all the way to 1000 yards and wound up used in the National Match ammo. Hatcher suggests the ignition characteristics were responsible.
Today, IMR 4064 is the IMR powder closest to the old IMR 1185, with grains 0.031"×0.083", and a 6.5% DNT coating. I have found it very forgiving of packing density changes. More so than IMR 4895, which has a 0.032"×0.056" grain with 5.5% DNT coating. The differences show in the graph below, taken from an experiment published by Dave Milosovich in the Precision Shooting Reloading Guide (Precision Shooting Pub. 1995, p.102). You can see that changes in IMR 4064 charge weight (horizontal axis) produce smaller changes in velocity (vertical axis) than the same changes in IMR 4895 charge weights do. This tells me the IMR 4064 burn rate is less sensitive to changes in temperature and pressure of the two. That should be good not only from the standpoint of being more forgiving of charge weight error, but also of temperature change. This implies better ambient temperature immunity as well. IMR 4064 enjoys a reputation for having an accuracy edge over IMR 4895 in .30 Cal match loads and was used in the original Federal Gold Medal Match .308 loading with the 168 grain MatchKing. I suspect this behavior is why.
If you want to try a spherical propellant, the Ramshot TAC suggested earlier would be my first choice. I spoke with one of their lab techs one time and he explained the coatings used were more modern chemistry than those used on the old military spherical powders and do not need the CCI magnum primer formulation to perform well. WC844, WC846, and WC852 military powders that are sold as H335, BL-(C)2, and H380, employ older coating technology that make them harder to light, which is why they do need it. But with the Ramshot powders, several sources have reported them doing just fine with the Federal 210 and other standard large rifle primers.