Sorry to dig this up again, but I've just had my barrells honed to suit my new IMD +040 pistons, and thought I'd weigh them to compare with the old ones.
I'm not sure what brand the old ones are, (auto & aero or something like that). Anyway the IMD are just 13 grams lighter for the pair including rings, pins, and circlips, so that further justifies my decision not to worry too much about crank balance.
They look great quality and the proprietor Adrian could not have been more helpful.
The big plus for me with these was that the +040 are actually a couple of thou larger diameter than the old +040s that were in before, (wear in the old ones or design in the new ones???), This gave me the option to get a couple of thou honed out of the barrels without going for a full size up rebore, thus preserving the possibility of a +060 for the future.
Chuffed with that result.
Jase