Thanks for jumping in nm9stheham. There is no sign of a ridge at the top and yes, as you say, I've used a bore gauge to measure 3 points to see if there is taper. I'm about to do it over again now to make sure but last night, there was about 0.002 (0.003 worst case) throughout. That would make the bore about 3.908 against the factory spec of 3.91.
