The only way to prove "sloppy bore" is with the special gauging equipment, or have some way to measure the force required to push a lead slug through the bore. (Varying force, inch by inch, means non-uniform bore diameter.)
We do know as fact that a shorter tube is stiffer than a long tube. Shortening the barrel might make the vibrations more uniform. And, if any "bad bore" is out near the muzzle, it would of course be removed.
Art