I used aluminum to meet weight requirements when I belonged to the N-SSA. They increased the limits about 10 years ago, and I started drilling and adding lead to bring the weight up. We won a number of championships with both weights. I resigned from that organization, and I now use it for American Civil War Shooters Assoc. competition. It works very well at 200 yards with light powder charges. For the long range match at Grayling I use zinc. I use a .020 windage. All projectiles have to smoothly slide through a 10 inch section of the bore liner. The base of the mold is not a section of the bore liner. If the bore liner was used it wouldn't provide enough clearance for loading.