Kirk. if you're heliarcing, use ER 70S-6 filler metal and a torch with a gas lense if you have to go back and touch it up. That will usually stop the porosity flare-ups. Once you have it tho, it's harder to get rid of. If you're just going to polish the bolt and handle and not blue or parkerize, you can use any 300 series stainless filler metal (ER 308, 316, etc and the porosity will clean up quickly. Makes a strong, tough joint too.
Good going; if it was easy, everybody would be doing it! Tom
Texas State Rifle Association Life Member
NRA Endowment Life Member
A big fast bullet will beat a little fast bullet every time