.002 or .003 gap requires all the dimensions to be consistent , and square , at risk of the gap getting fouled and dragging .
.005 is a good goal for mass production revolvers .
The transition between " desirable " and " not as desirable " is subjective , but lets say around .007 to .008 is not uncommon .
But less , for every mfg , there is a gap between " less than desirable " , and " factory wishing to repair or replace under warranty " . Every Mfg , not only Ruger .
Once upon a time , I briefly had another brand large frame .357 Mag , with a .010 plus B/C gap , that would shoot sub 1 inch @ 25yds .
It moved on to a good friend , and he eventually paid to have Bbl set back , because the idea of the gap bugged him .
I don't think I chronograph'ed it while I had it , but the difference between a .005 and
006 would have a significant difference in velocity .
( Yes , it was chronograph'ed afterwards , and he may have before . but due to his untimely passing , can't access his chrono records .)