The traditional method of removing a load from a barrel involves using a wooden dowel or brass cleaning rod to push the ball out. It's essential to use a material that won't damage the barrel. You can lubricate the barrel and gently tap the dowel or rod with a hammer to ease the process.
Another method involves removing the nipple and replacing it with a grease zerk fitting. This allows you to use a grease gun to apply pressure and force the ball out.
Some have also used a battery drill with a small drill bit to carefully drill out the center of the bullet, making it easier to remove with a wooden dowel.
Always approach this situation with care and patience. If you're unsure or uncomfortable with any of these methods, consult a professional gunsmith to ensure safety.