Hi Donna
Yes you do. I have cast cores for about 10 years now, and You don`t have to but the weight will vary a couple of grains if you don`t. That is I have corbin`s four cavity mould`s, and I can use them just out of the cast, but the bullets will vary anywhere from 1 to 3 grains, no matter how accurate I try to adjust the core weight from the moulds. Its time consuming and a pain in the A$$ to try to get them as close as possible for a certain weight.
I finally went and spent the extra money for the lead wire after reading about it on this forum, and have been more than happy ever since. The cost for pure lead in my part of the country is the same as buying the lead rolls of wire, so I elect to purchase the lead wire.
which ever way a person goes, cast their own useing lead mould`s or buying the lead wire, you still have to run the cores through a core swage die to get an accurate lead core weight for the bullet.
bullet maker