Wow, I view the Krag hand-guard rivet as a tough and tricky job.

You can shorten an overly long rivet before the 'peening' operation.

I had a rivet come out of a repro hand-guard once. I had to resort to fixing it with an aluminum 'pop' rivet. It was not pretty, but, neither was the Krag. (I could not figure out any other way to set a rivet without destroying everything. I put a dab of 'liquid steel' on the hollow rivet head to make it less obvious ).