Not quite the same meat but I 'adjusted' a 7.62mm No4 barrel muzzle that needed to be breeched in a but further to get anything like CHS. when the foresight block threads overturned by some way.

Just machined the lugs off plus .030" or so down to the end of the overturned lugs. Then machined a knackered .303" No4 muzzle to suit. Put 2x flats on the barrel, sweated the new 'sleeve' in place, aligned on the glass flat plate and nobody could tell the difference after it'd been through the phosphate and paint plant. Even had the bayonet lugs this time.

Still shot like a pig but 7.62 was cheaper than .303!