and brazed not welded.....due to thickness I think......Reynolds 531.......
Thing is a mig can do car panel thickness, bike tube is not thinner than that.
You won't be able to MIG a bike frame unless you make it from scaffold tube....! I have brazed and TIG'd a few in my time. I am building a stainless Reynolds one at the moment as a winter bike. That will be brazed as its not going to be painted and I want to have the braze polished and on show to contrast the stainless.