Subject says it all, inspired by a post in another thread.
I’ve tried some google-fu on this subject, but to no avail. There was a case of someone being arrested for bringing a gun to St. Johns in NY on sept. 26, 2007, where the gun was originally reported to be muzzle-loading. The confusion was caused by the fact that it was black-powder, though it was actually a breech loader. Here is the article- http://cityroom.blogs.nytimes.com/2007/09/26/armed-man-arrested-at-st-johns/
Probably hunting without a license, recently.
Amendment to OP:
Let’s say “crimes against property or persons” in the spirit of the previous thread.
All the time i would think. I work at Starbucks and talk to a lot of cops who come in. One time they got a call and had to run out. They came back an hour later to get the drinks they never got. We asked what happened. Apparently some guy dressed as a pirate with a muzzle loading rifle was screaming at people in a parking lot…
If an accidental shooting counts
I like that one:
“A battle re-enactment last month pushed realism to the limits: a retired New York City police officer portraying a Union soldier for a documentary film was shot in the shoulder, possibly by a Confederate re-enactor”
We could almost call that the most recent casualty of war due to muzzle-loading weapon fire…
Since I live in Massachusetts, I could lay my Schuetzen on this table without putting a trigger lock on and go and walk one step beyond the end of my driveway … for the win!!
But that would be illegal.
An elderly man (and gun collector) shot at a fireman with such a pistol in a Paris suburb a couple weeks ago. The fireman was not wounded, though.
The firemen were in the process of evacuating the building. The man’s excuse was that he had mistaken the fireman for his (female) neighbour :dubious: 
He was sent to an hospital for a psychiatric evaluation.
Looks like clairobscur may have it.
“I thought it was my neighbor…”
Gotta’ love cranky old men, though less so when cranky lines up with homicidal…