Hi 351
Does your lee loader come with a case-mouth belling tool? That's what you need to load your cast bullets. It's not that you bullets aren't the right diameter, they probubly are, but it's standard to bell the case mouth because lead will be shaved off the sides of the bullts. If the loader can't bell the mouths, perhaps you could bell them with a round metal punch that tapers quickly. You might be able to work the punch in by hand, and just open the mouth itself a few thousandths just enough to accept the base of the bullet. Once the base is started, the rest of the bullet will go in just fine. The belling will be removed once you crimp the mouth onto the bullet.
By the way, do your bullets have a gas-check on the end? I'm assuming if they are described as "gc cast blts", they are. When you load your bullets, make sure that the base of the bullet is no lower than the bottom of the neck. That is, the neck area should still be touching the gas check. The reason is that the blast of firing could potentially dislodge the check from the base of the bullet if it isn't held in place by the tension of the neck. If seated properly, the pressure of the burning gas will uniformly push against the gas check, which uniformly pushes against the lead bullet, resulting in the best accuracy.
Good luck, and get a hog for me.
Michael