This thread swerved more than usual and even faster than normal. Imagine my surprise.
Gas checks......I use fewer of them than I once did (back when they weren't luxury items). They can 'Cover a power of sins' (using Huck Finn's language) if your diameter or alloy isn't up to snuff in a given firearm; the bore will still be leaded, but you'll never know because the check will scrape out most of it. Accuracy will still suffer, though. Once I got a handle on dimensional integrity the alloy fetish diminished apace, also.
Gas checks are still featured whenever velocities edge up past 1300 FPS in either handguns or rifles, though. My default alloy has morphed from good old Taracorp 92/6/2 to 90/6/4 for improved castability in the microband Loverin designs by adding 6 oz. of tin to a 20# pot of 92/62--which I have A LOT OF.