I checked around at 'Modern Muzzleloading' some... seems this file knurling of bore size sabotless bullets is done by some on all copper Barnes X Bullets, TMZ's, etc.
BUT those doing so are guys using custom re-barreled muzzleloading guns with centerfire steel barrels installed.
Here's one quote from the site:
"You can go up in size a little by knurling the bullet (rolling it between two files), the coarser the files the larger the diameter.
One of the guys resizes 290 TMZ's for his .45."
Others do this up-sizing method in standard muzzleloading barrels using all lead bullets to achieve a tight fit in the bore.
You can get to the site here:
http://www.modernmuzzleloader.com/phpBB/index.phpTo view most of the stuff though you need to register.
If you're into high performance muzzleloading stuff MM is the place to find info on it.
Many members
here can be found
there as well.