Re: Barrel Lapping
I used Tubb's on a Tikka T3 Varmint and on a Marlin 336 and the result was a very smooth, polished barrel that had a noticeable difference in copper fouling. Not that the Tikka was bad, but afterward it was less and a lot easier to push a patch through. The marlin wasn't great to begin with and was much improved after.
Not a bad experience, but I don't think I have any measureable data to share.