Woody, I'm guessing it was the brass that caused the problem, as I have had limited success with thick brass and brass rod. Brass 'work hardens' which means that as you turn it down it gets harder and harder, and the wood is going to give up before the brass does! You might want to try turning it with a grinder, which will reduce the stress on the blank somewhat. (I've never done it but I know Paul M has, so he might offer some insights into the technique).
Pity, because that looked like it would make some gorgeous pen barrels! 
