I tried using small single-strand wire to get an idea of the size of the orifice. Looks like .45mm. Hard to be sure because wire sizes aren't very accommodating for .3, .4, etc. mm sizes.

I'd like to change to a .3mm nozzle. The existing nozzle looks like it was machined out of one block, so not interchangeable.

Now that you pointed me in the right direction, I found and the hot end/nozzle looks like #5, #7 or #8. So I'd like to change out the hot end for .3mm. It looks like just above the hot end there are two screws in the bottom of the extruder. If I loosen them, is it probable that the hot end will come out and I can replace it? I have not problem with the wiring aspect of the change-over, but is the mechanical aspect as simple as loosening the screws, pulling out the old hot end and inserting the new one? Or is there some alignment that needs to be done so it feed properly (if feeds fine now).

Also, given this type of hot end, any recommendations for a decent replacement?

Thanks for all of the help.