When I first learned about Krag rifles I came across many stories about that single locking lug and how it can break and cause a catastrophic failure and hurt or kill the shooter. As I looked more at that issue, and looked more at the way the bolts are made, it doesn’t seem likely given that the high axial shoulder is abutted to a steel shoulder as well as the handle itself being in a recess of steel. So I have just one curiosity, have any of you ever had a bolt fail on you or someone you know? Just how dangerous, or not dangerous, is this setup?

There was a test performed many years ago where a Krag was tested by Michael Petrov with the single locking lug removed from the bolt.  It was test at many times it's maximum pressure and held.  It finally failed when he used 30 grains of Bullseye. 

  (You need to Login

EDIT: Got beat to it!  See above.

As Petrov's write up describes - the Krag has the single locking lug plus two safety lugs - the bolt guide rib and the bolt handle within the receiver mortise. Any rifle can fail but the Krag failure mechanism is one of the safer.

And with the head of the case surrounded by steel, I've not seen any failures caused by gas getting into the action.