Hello
NO, They sure do not need the"M" fix. That was conclusive to the very first model 586's produced. This was a head space problem encountered after they did away with the recessed cylinders and went to the newer flush ones.I do NOT believe that the 686's were effected.This is my 586 and it was a very first issue. It does have this problem, but I handload for it and over sink the primers to take care of the problem. Best regards, Hammer It
All "no-dash" L-frames are subject to *possibly* needing the M modification. That would include 586-no dash, 686-no dash, 581-no dash, and 681-no dash.
Gixerman... wow.... there is nothing so stunning as a 586! These are truly magnificent revolvers.