Finally completed NYC permit process. I took my first purchase, a Ruger security six (1978) .357mag. I cleaned it, changed front site and went to the range. (BTW, bought used of course on one of the major websites). Took 100 rounds of 158g .38spl fmj. I had a locked cylinder about 12 times and about 40 failures. Line officer said try 6 rounds that I have (different manufacturer) but cylinder failed on 3rd round of his stuff. Took upstairs to the smith, he said timing was good, he tried it downstairs at the range and couldn't get it to fail. He did say he thought it was dirty down deep. Came home, sat down, followed vid on YT and totally disassembled. Cleaned to an inch of it's life and re-assembled. Dry firing everything is working as it should, but since I never did this before I am a bit scared I did something wrong and it's going to blow up in my hand next time. I am a pro mechanic in another field and extremely proficient with tools. I did find a tiny burr on the leading edge point of the hammer. I used 320 emory to clean and smooth it, and polished up to 4000 grit. I can't find any vids that address function testing on a revolver, so can anyone offer a pointer or two? Just trying to be a safe and responsible new owner.