He didn't move the front sight. That stub you see in front of the sight, is part of the liner. If you look closely at the pics, you can see where the mate lines are.
The job wasn't done correctly, for the type of barrel and pressures. That was a quick drill out and maybe ream job. The sleeve was turned from a blank, likely very close in diameter to the stub at the muzzle
The job wasn't done correctly, for the type of barrel and pressures. That was a quick drill out and maybe ream job. The sleeve was turned from a blank, likely very close in diameter to the stub at the muzzle