You're welcome. There may be extra material on the barrel extension in all three directions to allow for custom fitting.
The underlug looks OK to me. Sometimes these are welded on after machining the barrel, sometimes the whole thing is machined from a single block of steel.
As a possibly interesting side question, mine came with two fired cases in a little envelope marked with the serial number of the gun. I wonder how much good all that super-duper detailed record-keeping does if you change the barrel.
Terry, 230RN