If you have a proper reference regarding the accuracy potential of the M in a  Win Mag chambering please provide that web link As far as I could read there is a solicitation underway for rechambering M rifles and I could not read anything about accuracy requirements though one might suspect these rifles will not be exceptionally accurate since the M SWS is in essence an accurized or if you want to view things more critical a glorified Remington  hunting rifle    If you go on provided link httpswwwfbogovindexsopportunitymodeformiddcebcfbbbdfbfbeceftabcorecview and download Amendment  going through Download Solicitation page no direct link then you will get document PURCHASE DESCRIPTION  January  Revision RIFLE  WINCHESTER MAGNUM SNIPER WAY OPTICAL SIGHT AND CARRYING CASES M RECONFIGURED where you can find Targeting and accuracy  The rifle shall achieve the dispersion set forth below when fired from a machine rest  The average mean diameter of shot groups fired with and without the sound suppressor attached shall be less than or equal to  inches at  meters  MOA T  inches at  meters  MOA O  The minimum rate of fire for conducting this test shall be three rounds per minute This is really complicated work