Well it only took 9 months or so, but I finally got the M1888 back out to the range and got it on paper. Stayed at the 50 yard line this time out, and was able to figure things out. This was about at dozen rounds, holding at the very bottom of the target at 50 yards, hitting about 14" high:
As before with the M1873, very pleased with how this old warhorse shoots. Still going strong, 129 years later.
ETA I'm not ignoring the advice about the single black bull, I promise! I'm just cheap and already have a stash of the red targets, LOL.