It's easy, common is to use creosafe (could be mispelled) it is really woods metal with a melting point of about 180 degrees F. Melts in boiling water. Push some paper in the barrel and pour the stuff in the chamber. Push it out and see what you have. I've used Candle wax, you will need to oil the chamber up some to get it to come out good. Plug the barrel about 1/2 inch in front of the chamber, pour some in and see what you get. Larry