I don't know if this link will work, but this is me firing my Martini-Henry Mk1V on the zero range at Bisley about seven years ago. Let's see....

https://www.youtube.com/watch?v=hqeHwrAjxh4

I found that using coarse black powder is much more pleasant than using medium. This didn't kick too badly at all, quite mild actually, but using medium turns it into a spiteful *****. It's back off ticket now and I don't shoot it anymore, but it was a lot of fun for a few years.