Depends on who you talk to. Personally, I would not wish anything over .008". I prefer .006" as an upper limit but If I found a very desirable piece with .008", I would take it. If it was .010" I would pass on it.
Barrel-cylinder gap should be between .004" and .012". About .005"-.006" is "ideal", but I see a lot of new guns with it more towards the upper limit, and a few with very small gaps.
