seeing as there is now less metal at the muzzle, that must therefore mean that there is more room for air, and as air is significantly more dense in your part of the world due to the moisture content attracting pheromones and associated carbon dioxide, allied to the impact of the location of the barrels impact on the earths orbit, due to the removal of the metal reducing the prior subsequent orbitting speed by one tenth of .7689 second this therefore would result in the barrels being heavier - simple really. Did any body REALLY read this far???? ;-

seriously though, I would be interested to know the difference - educated guess 1 ounce less !

Jonty