I don't have much experience with the Ruger Blackhawk in .30 Carbine and none (up until now) shooting it for serious accuracy off a bench. I had plinked with it a few times.
Point being, I really didn't know what kind of accuracy to expect, but I did know that the accuracy I was getting was horrible with the Herter's ammo. Even if the gun itself isn't a tack driver (it may be for all I know), 8" groups (or so) can't be normal.
You know the rest. In the books you have read
How the British Regulars fired and fled,
How the farmers gave them ball for ball,
From behind each fence and farmyard wall,
Chasing the redcoats down the lane,
Then crossing the fields to emerge again
Under the trees at the turn of the road,
And only pausing to fire and load.