soldering underlugs

[Mark Y]

What type of surface prep of the barrel and the under lug should I do before attempting to solder a lug onto a barrel?

[Dr. Tim-Boone]

Assuming it is a round barrel, I just sand the area on the barrel and the lug to make sure they are  clean, coat both sides very thinly with solder paste and heat the lug briefly with the torch till I see bubbles coming from the edges.... 20 seconds?

[cmac]

I'm sure all have a bit different method. I lightly file the lug and barrel instead of using sand paper. With the idea that it gives the solder more to grab

[B.Habermehl]

File or sand the mating surfaces back to clean metal. Do not touch the surfaces with anything but flux. I'm old fasioned and like to tin the surface of the underlug first. Coat the barrel portion of the joint with some flux. Then clamp the parts together and heat primarily the barrel till the solder liquifies. I usually touch the joint with solder from the oposite side of the heat source, the solder will suck right into the joint twards the heat. Allow to cool naturally, done. I use common lead free plumbing solder and flux with no problems. Mostely because that's how I learned to do it in the first place. Lots of ways to skin a cat.  BJH