Never in my life have I seen a hammer blow out like that Cayugad. I can't imagine the pressure mechanics that would do that rather than just kick the hammer back to half cock. Something real funny had to be going on. I wonder if it's possible the bullet was not against the powder, with maybe an inch or so of air between the two. Anyway, send the hammer to TC and they will send you a new one (you may as well ask for one of the ones offset for a scope).

When you said the rifle kicked like a mule, were you referring to just that last shot or to all of the shots with the 100 grain RS load? Also, I'd be thinking about replacing the nipple.