Without getting my book of figures and a calculator out I tend to thinking that taking 10 thou off the inside diameter is not going to make a significant weight reduction.
I would be weighing the 3 gun component parts and comparing the weights with other guns of more suitable weight.
It could be that you have a big solid action that someone sleeved to a short barrel length rather than a light action with a unnecessarily heavy barrel set.
Some vintage guns were made HEAVY, some light as wands.
As CJO says, balancing the gun can make it feel much lighter.