36 gauge is .506". If the bore is that big it should have been stamped as a 36, not a 40. As stated earlier the 40 stamp would indicate a "Bore" that would accept a .488" gage but not a .492" one. This would give groove depths of from .007"-.009" per side. I think this would be normal for a Black Powder rifle shooting lead bullets.


Miller/TN
I Didn't Say Everything I Said, Yogi Berra