I pulled some powder coated bollits out of my test barrel (filled with rubber mulch) and found that they had some of the coating scraped off closer to the base of the boolit, well below the case mouth. It's not scraped all the way around the boolit, only about 20-30° around the diameter. This is from two different firearms - a Glock with an aftermarket barrel and a Ruger PC 9 carbine.
I size to .357, bell the case mouths, crimp separate with a taper crimper only enough to take the bell out. I have pulled boolits with an inertia puller and verified that the coating isn't being damaged in the loading process. Using a bore scope, I can see the coating that's left behind at the sharp edge at the forward end of the chamber/throat interface.
Can this only be fixed by having the barrel thoated? I don't think that the Ruger is Melonited, but the aftermarket Glock barrel is, making the surface very hard. I thought about trying to put a small radius in there with a cratex point, but concerned about maintaing concentricity. Any ideas?