The fact that the bolt was open certainly saved him from serious injury or possibly worse. If the bolt had been closed the force of the explosion would have had only way way to escape.

Up the barrel. eek

But then again how would you get the live round out with the bolt closed?

"You cannot invade mainland America. There would be a rifle behind every blade of grass"
~Admiral Yamamoto~

When the people fear their government, there is tyranny; when the government fears the people, there is liberty. ~Thomas Jefferson~