Numbers...i'm in S.A. myself...I've visited a couple of shops here. Both have advantages and disadvantages. I don't know about their smithies except one does tend to ship out his work to others...but here they are anyway.
Don's Gun Sales- 8517 Perrin bietel. (210) 657-4550.
This is right on the corner or PB/410. In one of those strip malls. Not a large selection of firearms and they seem a bit steep but nice, fairly knowledgeable people.
Nagel's Gun Shop...6201 San Pedro. 342-5420
This place is packed with crap...two people can't walk past each other in there. Had to go there for ammo for my Makarov and I'd bet they would lead you to the right smithy. They are about two miles south [I think, same side of 410 as the mall that's there. I hadda WALK to it from the mall so I KNOW it's two-miles] on the right.
Other than that...There was a place in Austin that was the best I've ever seen. I'll have to call the Vet I used to work for there because I can't remember the name or road-I can FIND it with no probs...just the names elude me.
Alamo...one of my favorite places is Austin. Ok....Sorta North Central Austin...take the W38th St exit off the highway...drive a couple of miles...you come to a place about a mile before Mopac. There is a grocery store on the left...a Safeway last I knew. If you drive thru the Grocery parking lot-you will hit W35th. across W35 is Brykerwood Veterinary Clinic. [[Where I had a life before blindness]] Ok...turn left on W35...it curves down and around a hospital complex...you come to a light. Go thru it to the next street. [[as if going back towards the interstate.] The gun place is either right there or within a couple of blocks to the right on that street. Like I said-I'll get the bloody name and number for ya. ~LOL~
Check the link provided by GrandmasterB. Alex Hamilton is one of the best pistolsmiths in the U.S. and former pres. of the APG. Only downside is that he may not be cheap and it may be hard to get him to work on your gun.