I've had about 6 true pencil barrels and can't really see where they could shave any weight from them without compromising the barrel.
I'm not sure what you mean by shaving weight off a pencil barrel. I assume you didn't shave yours.
How much did they weigh?
As for the BCG, I'm not going to compromise reliability by messing up that. I don't know exactly how Midwest Industries got all the weight off their lightweight rifle, but if they did it by making it unreliable in some way, then I wouldn't want to go there.