If you consider the old defination, 3F is for Pistols and rifles up to and including 45 caliberbeyond that it has always been used for short barrels and plinking. Two F is for rifles of 50Cal and up and for getting accuracy with heavy loads. Personally I use 3F in my pistols and 45 cal Hawken. For hunting I have always use a big cal. and a heavy[120 to 150gr FF] load to get the caliber & volicty combination that gives hydrostatic shock. Lee