It was always a theory of mines that any type of weapon used by any z warrior always had a power level not by itself individually ,it would simply gain one equal to the power level of whoever held it in their hands which is the only plausible explanation of why weapons would be effective in the first place especially since there's no explanation provided ever in the series how an ordinary sword with zero power level of its own could slice through ape vegetas tail or mechanical frieza but not through super saiyan gokus index finger when trunks swunged his sword at him multiple times. You pretty much just go along with it.