This has been hashed and rehashed here many times, but deserves repeating. The weight of the gun is far less important, in terms of how easily one can adapt to it, than where that weight/mass is located in the gun itself. Don Amos spun that little .410 pictured above about a year or two after I got it, and got proficient with it. He found that, and I quote him, "It's moment of inertia is almost identical to that of a 12 ga. English game gun". I didn't understand and he explained it to me. When more of the weight/mass is in the extremities of the gun, i.e. the buttstock and the barrels, it increases the effort needed to swing the gun (MOI), or move it around it's center. That is exactly what you need in a very lightweight gun, for it to slow you down in your "move". An English game gun will be heavier in the action but lighter in the barrels and butt, thus causing the MOI to be different than a more "normal" double.
In the case of the gun pictured above the action is a lightweight alloy. This causes more of the percentage of mass to be on the ends and makes it handle better (slower).
