I gave my son a .54 cal TC Hawken some years ago, but between high school, college and a few missed opportunities, he hadn't connected with a mule deer - until this weekend. He had a doe-only tag, and we spotted one in a draw on public land above some orchards. We hiked around the draw to the top and came down to find she was still there. She stotted thirty yards or so, and stopped when I whistled. (I couldn't think of anything else to do!)
The first shot (there were two) entered just behind the rib cage and knocked her right down, but she got up and went over the short horizon before he could reload. The blood trail was easy to find and follow, but it looked too dark so we decided to have a sandwich and wait about 90 minutes. About 100 yards after we started tracking again, she got up from a bed and my son made a quick offhand follow-up shot from about 60 yards.
He was using a 425 grain, 54 cal Great Plains bullet over 90 grains of GOEX fff black powder. The bullet expanded to .89 inches and retained almost 100% of its weight.
I don't know how much the deer weighed, but it was a large doe and seemed to gain about fifty pounds while we were dragging it out! We have been hitting the muzzleloader hunts pretty hard over the past couple years, and it was great to see him get his first mule deer with the Hawken!