Fair enough then, I'll make this my closing post.

For me this thread has been educational. I've found several witnesses to this kind of event - the broken bolt being the odd one out, from the cocking piece kicking back to cock a rifle to actually been blown out the back of the bolt (not confined to Lee Enfields). Twice with one person with a 1903 Springfield. The first struck his brother on the cheek with force, missing the eye, the second shot through his sleeve into the brush (fired from the hip), both instances with pierced primers.

What I need to know now is what causes pieced primers in the first place.

Thanks all for making this an interesting thread.