The tube wall is .090 thick. With the erosion I've got after 1000 rounds it mite make it to 3 or 4 thousand rounds. I got mine from Bud's in Nov. 2017 when they first reduced the price to 1360.00. I sure wish someone else will measure the orifice in the barrel itself, it's easy just remove the gas tube, there is a hole in the bottom of the gas block that lines up with the barrel orifice, in mine a 7/64, .109, drill bit will easily go in so the hole is probably closer to .110- .112.
If you look at all the pictures of the bad erosion you can see the larger diameter of the wear. In the picture from 2015 with 10,000 rounds the wear is just around the orifice itself. If the problem isn't with the gas tube maybe they sent some barrels out with the barrel orifice too large.
Just got off the phone with CZ Warr. again. Asked him about barrel orifice size and if these were US barrels, he didn't know the answer of either. Just kept repeating that this was a wear item and amount of wear depends on what ammo, atmospheric conditions, cleaning regiment. There not going to own up to anything. I told him about this forum and AK Files and to take a look.