Re: diy carbon barrel sleeve?
Your thinkin' is a bit out of the box, but just a bit. This would be an interesting project.
There is a gunsmith in Rexburg ID who has been playing with an idea similar to yours but with a different object.
He's rigging an aluminum sleeve over the barrel in a manner that allows for tensioning the barrel to tune it to optimum accuracy.
So. . . it seems something like your idea may work if you're willing to go through the effort.
I may be the slowest guy on the mountain . . . . but . . . . I'm on the mountain!