I had a friend that used to do this to some of his reloads. He found that whatever .44 lead hollow point bullet he was using for his .44 Mag reloads, the cavity was perfectly sized for a small pistol primer. He would carefully put some powder into the cavity, then carefully glue the primer over the powder. Made a pretty impressive flash when it hit the far side of the stripper cut we used to shoot in but scared the crap out of me. Of course, this is also the same friend that used to brag that his .44 Mag reloads consisted of dragging the case through a pan of powder, brushing it off flush with the case mouth, then seating the bullet. When he shot his S&W 629 loose shortly after he got it and had to send it back to S&W, he quit doing things like this and now is pretty normal. Well, his reloads are pretty normal, anyway!
Bub