I admit that the guy that bored mine out wasn't a machinist as he claimed to be (and many a paintball player gave him positive reviews...sigh) and left a LOT of machine marks during the boring. This made the issue of the thin wall even worse. However, think about the theoretical maximum thickness:
(0.875-.753)*.5= possible wall thickness of 0.061"
Now, factor in the trapezoidal thread: ACME 0.860-1/14
Assuming no undercutting is done (I don't have phantom barrel atm), which there should be, then we have the following:
[(0.860-1/14)-.753]*.5= a wall thickness under the thread of 0.0177857"
Now that's pretty damn thin. I'm not comfortable with that. But wait, there's more!
There's that o-ring groove, isn't there... Someone put some calipers on there and report back.