WW1 infantry rifle = Gewehr 1898/Gew98 = 29" barrel, slings vertically on shoulder, straight bolt handle
WW2 rifle/carbine = K98k (Karabiner 98 kurz= carbine, model of 1898, short barrel) = slings sideways on shoulder, 23" barrel, bent bolt
Commercial rifles = M98 = Mauser 98, describes the action type, rather than a particular configuration of rifle. For commercial sporting arms, concern is usually more for parts fitting than for standardization of a military arm.