Partial thread derail, but I took my AR-15 in to Allegheny Gun Works this afternoon. I concur wholeheartedly with Kaso's recommendation. The staff is very attentive, very knowledgeable, and friendly without being "too friendly." And they are honest too. I explained to the gunsmith (Josh? I didn't think to get his name) that I feared I'd over-torqued the castle nut and receiver extension and asked him to take a look at them. He did so, and told me that I had over-torqued it and had "tweaked" (his words) the threads on the receiver extension a little as a result, but not enough to do any damage to the rifle or make the extension overly difficult to remove, so it didn't need to be replaced, and everything else on the rifle looked good. They didn't even offer to sell me a new receiver extension.
That right there sold me on him and on Allegheny Gun Works in general. It was pretty clear that I really didn't know my stuff, and they could have said that I'd damaged the receiver extension, castle nut, receiver extension, or even the receiver (or some combination thereof) and tried to sell me replacement parts that I didn't know enough to know that I didn't need. But they didn't. They only charged me there standard (and very reasonable, in my admittedly-uneducated opinion) fee to remove/replace the receiver extension, which they torqued and staked to spec.
So two solid thumbs-up to Allegheny Gun Works. I think I'll stick with my usual LGS for ordering parts and accessories, but I'll be taking any gunsmithing work to AGW. I've been thinking about having some work done on my Range Officer Compact (AGW offers Cerakoting too), so maybe if/when I have the $$$ to do so, I'll take it to them.