Beetle, I am not doubting that they now use 5.56 chambers. They used to use .223. I helped several of my deputy's put together AR's several years ago. Some wanted to go the cheaper route, so they ordered the Wilson barrel from JT Distrubiting. I also personally ordered a JT upper, an FN A2 receiver, with a Colt A2 USGI barrel. I had, and have not had any trouble with my barrel. It has even been used to try out the departments M16's which were having cycling problems on FA due to improper gas port diameter. On the other hand, 3 JT Wilson uppers had numerous failures to extract. I am a Colt certified armorer. I do not cling to the Colt horse though. I have a Colt A2, and a BM M4. I have another upper with an FN upper from JT. The problem is, for reliability, in personal defense, I have found non-chrome lined chamber/barrels to be a definate liability. I teach Tactical carbine/urban rifle not only to my department, but to all the PD's in the county, as well as the Park Service. I have taught the M16 series of rifle since 1975 both in the US Army as an AIT instructor, and now as a deputy sheriff. I have a pretty good idea of what does, and does not work. No, I do not think I know it all, I don't. I do know, however, that I will not risk my ass on a POS Wilson barrel, when for not a helleva lot more I can get a milspec barrel.