I shoot a sleeved William Powell and it is a lovely 16GA gun. If you stop and think about it, many guns today are built on mono-block actions and that is basically sleeved, so done properly I see no problems at all. I try to shoot low pressure loads in all of my guns just because I don't like recoil and the light guns I shoot don't deserve the pounding the high pressure loads put out. Besides, I have found the low pressure loads pattern better and kill just as well. I've never heard a grouse complain.
With all due respect, a sleeved gun IS NOT a "mono-bloc" gun. A mono-bloc is typically a single piece steel forging that a set of tubes are inserted and fixed into. The remains of the flats of a set of barrels that have been sleeved were an assembly of parts that were brazed, soldered and otherwise joined. It can not have the structural rigidity of a true mono-bloc.
Best,
Ted
