Mine liked 71.5 grains IMR4350, GM215M primers, once fired R-P brass. Best group .428" worst just under .750". Chronied at 2900ish at 6800 ft elevation.
Seated .010" off the lands.
The only reason I quit them is because of a rash of tips breaking off in the mag. One in .338-225, two 7mm-140, one .308-180.
I think the BC of .550 is overstated, but did not play around with them long enough to test it.
Hope that helps.