Interested in getting a GB and am wondering how accurate it can be with a scope. It has metal frame so I supposed adding a side mount should be relativly easy? I have no doubt the GB is accurate, but since the nose is by default touching the barrel and every thing does heat up during firing, how much will that affect the point of impact? (a frame-mounted optic doesn't track the direction of the barrel) now if the optic is barrel mounted then it will be so much easier, but then we need a custome long barrel (possibly need 8": 2.5" for the optic mount to clamp onto, 0.5" for threading for brake). Any input will be greatly appreciated. First hand experience only please, though.