I have a barrel that had a slot cut in it to a point that it appeared dangerously deep, So I wire feed welded on it (polishing with a SS wire wheel after each bead was laid down) until I had a full barrel diameter and then I lathe turned the barrel and milled a proper sized slot in the barrel and re-blued it.

It's a .223 barrel.  It looks good but do you think this method is sound? Or will the thing blow up on me?

The slot was for the front handguard retainer. (about 5 inches up the barrel and 2 inches from the muzzle <Krinkov barrel)

The guy I bought it from had hacked this slot (probably with a dremel) deep enough to come within about .150inch of the side of the bore.  I thought the bore would be horribly distorted by the welding but I tryed anyway and welded a little bead at a time (to avoid melting the bore) and when I was done the bore still looked perfect. (but I don't know if the wire feed weld rod will hold as well as the barrel originally would have.