TL;DR version - turned a heavy barrel down to govt profile.  Took more than intended off from chamber end.  Want to know if it's still safe.

Longer version with details:  

Took an older hbar barrel that I had laying around and turned it down to ~govt profile on my lathe.  At the chamber end it tapers from .980" down to .660"  

However, I mis-read the drawing I was working from, and cut the taper at 20 degrees instead of 10 degrees per side (20 total).  I caught the error, but not quite soon enough.  As a result, I have plenty of extra .980" section, but then the barrel reaches the smaller diameter of .660" about 1.350" from the bbl extension, instead of 1.500"

Comparing dimensions after the fact shows that I have a very small section at that shoulder, about .15" long, where the barrel wall is up to about 0.016" thinner than in the drawings.  


Does anyone know what the minimum safe dimensions are, or have data that would suggest whether this barrel is or is not safe to shoot?  

.016" isn't much. One way to be sure if it's safe... Ratchet strap the rifle to a tree use a ripcord, and fire a round, inspect barrel and brass, fire 2 rounds, inspect barrel and brass, then fire a full 30rd mag as fast as possible, allow to cool, inspect. If nothing is out of ordinary after a full mag dump, it'll probably be ok, like I said .016" on the outer profile isn't very much.

Look at the pencil barrel specs and see how they relate to your barrel. Knowing that the pencil bbl is noticeably smaller in OD, it will give you a good indacation on how far you went/ want to go.

Threaded ends are a minimum diameter of .4935 with no safety issues and pencil barrels are .570 forward of the gas block. If I am reading your post correctly you are saying you have cut to a .644 diameter which I would say you have plenty of room to spare. Maybe some fluting is in order?

.016" per side is not much at all.... I would hate to think that extra .016" is all it takes to keep a  govt. profile barrel from blowing up.

I think you will be fine.