I've never had much luck target shooting with Blackhawks, even the Bisleys.
Very happy target shooting my GP100 and especially my Freedom Arms .357.
My best group limit seems to be just under 5" at 50 yards. I've done it a few times with a USP .45, a .38 Super 1911 and my F/A. Most of the time I blow it with a flyer or 2.
Shot this group at 25 yards with a Glock 29 converted to .40 s&w and plated bullet handloads. I'm sure the flyer was my fault.