The 15-22 owners manual didn't originally have lists of recommended/not recommended ammo. It was around mid 2010 when someone here noticed it being published. S&W states "primer sensitivity" as well as not recommending any subsonic ammo. My guess is that the "tests" and recommendations being put in the manual were a result of the great many returns of 15-22 suffering OOB issues. After S&W started installing new springs in the 15-22 then the OOB reports here pretty much stopped.