I don't have it in front of me right now... but, when I was doing the basic fit up to see how everything lined up and started shapeing sanding etc... the inlet area for the tang is deaper then the inlet for the barrel, by about a 16th to a 32nd. once the tang is seated and screwed down and tight, the barrel won't "close" it strikes the area that is not as inlet, and I am afraid if I put enough preasure on it to take it all the way down, something (stock) will break.If I leave the thru bolt on the tang loose, I can set the barrel all the way down in it's factory inlet, but then the tang is proud of the wrist by about a 16th, looks/feels like... a buddy of mine built one not long before I bought my kit, he built up the area under the tang in order to make his barrel close, works but as I said looks like..
so near as I can tell, the answer is to take the channel down a bit.. again it isn't in front of me, but when I was home last and working on it, that seemed to be my best answer.