They used both the Long Lee Enfield Military bbl shape/contour (cut to appropriate length) and also the same of the SMLE No1MkIII bbl.

The former is the most common and the heavier profile of the two.

I have Lee Speeds with both bbl styles on them, but packed away.
If I can get to then I will pull them out and get some measurements.
Someone over on NitroExpress.com on the 'Lee Speed Forum & Archive' might be able to help in the meantime.
Good bunch over there.