if they're fish weights, depending on the age, they're most probably hard. this isn't necessarily a bad thing- you can shoot harder than 'pure lead' but you'll have to tinker with the ball / patch relationship and you may or may not get results that are as accurate as shooting with pure lead.
what's important is that you go through the dance of working up a load which gets you the best result. to this end, i would recommend that you get a gadget (one can never have too many gadgets) as a bullet stop which will allow you to recover the lead. this way, you won't find yourself in the position of being almost out of lead as soon as you get a load which make your gun a tack- driving machine.
if you haven't already done so, i recommend that you get Dutch Schoultz' monograph. it's money very well spent.
good luck
go forth
make good smoke!