I have a RSB that's on crooked.
I want to pull it and have the notch in the barrel welded up so I can reset the RSB on squarely.

Anything special about having the notch welded up?  Any particular "type" of welder I should take this to?

Have a picture?

You don't need to weld it up. Just drill it over size and use a larger pin.

The original pin is .160 and the hole drilled is 4mm(.1575), the max I would go is a .1875(3/16) pin in a .185(J) hole.

I recommend soldering the hole, not welding it.  Silvaloy 45 silver solder with Staysilv flux.  

The next oversize is #21, then #20, #19, #18, and 11/64.  No way should you ever need to jump all the way to a 3/16"

I gave him the starting size and a maximum I would go. It's his job to find something in between.
When some people can't get pins to move they tend to break out the drill. I have seen some really buggered up holes and the need to go big.

If you have it welded have it TIG welded. You can control the amount of heat you are putting into your barrel and can dab it in .
Spot it, let cool, spot it again, repeat.

Braze or solder you will need to heat the area of the barrel up to around 1200F to get the solder / braze to flow.

I do not like putting large amounts of heat on barrels, YMMV.

Tig welding is about twice the temperature of solder.  

Localized, if you know how to TIG weld.
Brazing or solder you need to heat the entire area 1200F + and high temps and precision tolerances like barrel ID's or plated bores is not a good mix.

Meh - I've been tig welding and silver soldering guns for 20 years.  I understand what you are saying.  But the method you described is known as "piss poor welding". Without the substrate going molten, there will be a flaw at the juncture.  You're not laying the filler on top of the substrate, you are mixing them.  That's the whole point of the puddle.

I agree that often there is a good question on whether silver soldering or tig welding is most appropriate.  I use both techniques almost every day.  And there are a variety of factors that motivate me to pick one over the other.  But the temperature localization of a #00 tip on an oxy/acetylene torch is  far different than some bubba with a can of MAPP gas. For that, yeah - the whole area is heated.  But I assumed we were  comparing two professional ly executed techniques.  While not quite as localized  because it takes longer for me to reach 1200 with a #00 o/a, then to reach 2200+ @ 75 amps on my tig, it remains twice the temp.  And the o/a has a significantly lower temp even a few millimeters away from the solder point.

Remember, prior to WWI, welding was not an option - all gun parts requiring that type of connection,  were silver soldered.

The only thing "piss poor" is someone that cant weld and your description of "substrate not going molten" describes it perfectly.

Building up an edge is a typical die / punch repair and is a daily task in manufacturing.
Its a pretty simple and basic repair.

(Simple TIG job)

Technology and processes have changed just a little since prior WWI........LOL~

(sigh).

ok.

I know I'm not a master welder, but I think i can tell the difference between welding metal, and laying a bead on top of metal.

And yes, technology has come a long way - yet guns like the Sterling SMG that were soldered together, haven't fallen apart because the solder was "too hot."  Because it's not.  HK triple-frames are soldered to the barrel.  Lot of other examples.  Mauser RSBs,

By the way, this is a solder job I did a few weeks ago, to re-position a front sight.