Harryredchow wrote:Take the barrel off before even attempting a job like this. It will be much easier and less chance of destroying something. For the cost of a base gasket it will be worth it.

Hell no! not unless you snap an easy out in there.

I avoid easy outs as much as possible. Especially if there is part of the stud left to get vice grips onto. If vice grips can't get it out, sure as hell an easy out wont.
Spray CRC from the top side too, that hole goes all the way through as you can see in your picture.

If it must be drilled, get a left hand twist drill bit 3/4 the diameter of the stud (use cutting oil), by the time you drill all the way through the length of the stud it should just about twist itself out.

Mild heat on the surrounding aluminum, freeze spray on the stud. Easy outs are the devils tools. Easy outs are hardened steel, but it doesn't take much to snap one. Then you are in for a very expensive repair.