Ranch Roper,
I'll try to pull the reins in here on my overly chatty tongue (I hope!). Can't make a promise, as I could
write a bunch about your range report. I thought it was
excellent in a variety of ways.
Your first target was very, very good, but I thought the second one at 200 yards to be even more impressive. And especially so because, as you said,
"It's a tough read at that distance. That 12" target is a dot. 200 is a real stretch for me." Agree totally on all three comments you made. The best is that you went for it, even though it was a "real stretch."
Here is my bottom line, RR. If you enjoyed this long-distance shooting, I'm certain your results at a 200 yard target will much improve after this summer spent practicing at that distance. You handle your 1860 with much good skill as these two targets display. I'd be right there (if I could) shouting support for every bullet you send down range.
Lastly, I must admit that my excitement ramped up when your Range Report so easily reminded me of the two summers I spent learning and shooting long distance with my 12-ga Benelli smooth-bore pump shotgun (1-oz. slugs). Nothing but an enjoyable challenge, and
very much fun the better I got at it. My keeper photo is of a 10"-square black steel target. (If you'd like to see that, I'd be glad to post it within your thread here --- don't want to just steel your thunder).

I only placed one slug out of five on target (barely so) at 200 yards, and it was an exciting range time for me. Without a doubt, I know you are a better shooter than I am. I'd simply hope you would experience the same if you keep on. I'd say "go for it." Yippee!
Finally, my advice is to wait on the 300-yard target board for a while; first wipe out the 200-yard board; I know you can do it!
Have much fun --- enjoy.
PT7