I firelapped with the Beartooth system. Using 500 to 600fps lead slugs impregnated with 320grit, it improved the cleanabiliy as well as halfing my groups. I honestly don't have any impression of the Tubbs system other than I have seen positive remarks. I used the Beartooth system to remove constrictions that are present in stampings and dovetails of the barrels. My gun is the H&R Buffalo Classic. I have done many other guns I intended to use cast bullets in. Jacketed groups improved significantly as well. I have not lapped anything but Marlins, a couple of Ruger revolvers, and that H&R.
There is a slight throat erosion, that in some cases, helps with the allignment of the bullet. A higher intensity cartridge may be tougher on this throat. I surely would wonder. On the other hand, I have over 11,000 rounds through my Marlin 1895 since lapping it, and the accuracy just keeps getting better and better. I also have very little cleaning to do after a season of using the gun.
Gun Test magazine (online), did a test on the system you are talking about. (or one similar) They were positive, but did say it wasn't for every gun. Used on guns where the accuracy has diminished, or there has been some rusting and the user may have little to loose. In a newer gun, I would use it in the case of a hopeless situation (lack of accuracy), if it was a higher intensity cartrdge.
