Those are tapered screws and the head has broken off, you can not tap it through from the top. It is going to be tricky getting that apart. I would think long and hard on that one before proceeding. You might try an easy out, a skilled welder might be able to tack on enough material to back it out, last resort would be drilling it. Not a fun job.

http://www.bertramandco.com/
Booking African hunts, firearms import services

Here for the meltdowns