If you want to use lead bullets it is ok with this stipulation. You need to drive them at a reduced powder load and check your barrel often for leading. If you get the combo right it won't foul the barrel with lead. What happens is if the force is to great the bullet will skid through a section of the barrel because the metal isn't strong enough to grip the rifling in the barrel. Most lead bullets are an alloy of lead and tin or some other metal or metals. This will harden the metal and help prevent leading.
The short answer is you can shoot lead bullets all day long with no lead issues if you take the time to learn the tricks and keep an eye on your barrel. Most reload manuals have reduced formulas for cast lead bullet that are good formulas but they are contingent on bullets of a correct hardness so alway check for leading.