Bruce and a few of his current and former staff are members over at SiGForum. Have been for years. When it comes to metalurgy in general and applications in gunsmithing, Bruce is a HUGE resource of information. I have not had any work done, personally, by the Gray Guns staff but would NOT hesitate should I ever have the inclination. He has also in the past gone over models that were having a large number of problems, identified what he felt were the significant aspects of those problems and not only got the fixed for those that sought him out, but sent his inspections, finding and recommendation to SiG to conside. Straight up guy that doesn't blow any sunshine, IMO. BTW, my only personal contact with him has been very limited and via threads and a few posts over at SiGForum.
As for the mags, Dave at DKMags.com has the 18's but is also out of the 20's. I've dealt with him several times in the past and have no qualms recommending him.
Tom and his staff at TopGunSupply curerntly show them in stock: http://www.topgunsupply.com/mec-gar-...azine-afc.html Cannot recommend any vendor any higher than I do Tom and TGS. Their service is beyond excellent and you will get what you order faster than you think you would compared to anyone, even a short drive into town to buy whatever it is. They ARE that quick.