If you read Armalite's Tech Note #73 and do the math, you'll see that the gas tube is exposed inside the receiver approximately 1". I have checked many AR10's and that is where they fall. At the risk of sounding like a know-it-all, that is why I asked the question I did, but Powerman only showed pictures of the gas block and the slight leakage, which means nothing whatsoever. Like I said, check the gas tube protrusion inside the receiver, that's what matters. Just my 2¢