That's a great idea in revamping your used, M10 4" R/B. Personally, I still regard my M64 4" R/B DAO as an fully capable example of a 'Fighting Revolver'. I bought mine back in the late 1980's as an 'exemplar' to replace our older, assorted Revolvers. At the time, we had an assortment of 2" & 4", Colts & S&W's in service, & I proposed my example as an standard issue model. However, as we now know those days saw the initiation of the semi automatic Pistol for Duty, & the Administration decided upon the Sig P.226 in .40 for standard issue. But, as I had purchased my 64 as an POW, it was mine to keep & cherish, which I still do. Sometimes I wish it was a 3", but I already have my 3" M640, so it's just not worth the expense of rebarreling. I have always preferred the S&W R/B configuration over the S/B, & all my S&Was are now Round, even down to my 4" M21, .44 Spl. My only
exception remains my long owned 6" .22 LR H.E., circa 1915 +/-. Good Luck with your pending conversion, although I fear what it's going to cost you when all is done !!

Best, Dom P. / dpast32