I am just a hobby builder, but sometimes a blind hog finds an acorn. Make sure the barrel is truly sitting all the way down in the inlet. If you have inletting black, put some on the bottom flat and press the rear of the barrel down firmly. If there is no black on the wood, you are not all the way down. Instead of inletting black, I now smoke the piece with candle soot by holding the piece in the flame for a few seconds. It works well and is much cleaner. Sometimes a stock may warp after it is made causing the rear part of the inlet to appear deeper than needed, or as you have the barrel may seem too high. I always remove the breechplug to fit the barrel as the stock as the part in which the tang fits is sometimes higher than need be. In that case, you will need to deepen the tang inlet. Always look a whole bunch before cutting or filing.