I have measured both Ballard and Micro groove barrels and there seems to be no difference in rifling height. All have measured .003" high and the only difference is the number of grooves and lands.
The advice to use a larger diameter bullet holds true for both. Seems they bore the barrel with the same tools and pull a button through. I have yet to see a Ballard except originals that have deeper rifling.
I made my 30-30 molds to be .311".
When I had the .35 Rem, cast never shot good since the molds were not large enough. Lyman mostly. At the time I did not know about larger diameters. Close to 60 years ago. Now I wish I still had the Marlin. .357" was too small so a .360" could fix it.
Old original marlins had deeper rifling.
Same is true for the 45-70 where a .457" or .458" is too small and most need .460.
