My BIG Vaqs had .002 or 3 gaps from Ruger. If I didn't clean em often enough, I'd get enough lead on the face of the cylinder to make em drag even with smokeless.
A pard told me that the cutter for my Lyman Universal Case trimmer makes a fair forcing cone face cutter. I took him at his word and using thumb pressure to hold it snug and fingers to turn the four bladed cutter, whittled the forcing cone faces until two sheets of printer paper would clear the gap, but three would bind. The paper is .003 thick, so I'm somewhere around .007 or .008. All fixed, no more drag issues, even with BP, and my "monster" non-CAS loads throw a little more fire now, but only lost about 50 fps.