One of the great things about casting is that you have a seamless drum shell when your done with the process. Drums that are rolled and welded are quite often egg shaped and the weld is always visible even after you brush or polish it. The reason why this happens is because your super heating and melting the area your welding and changing the properties of the metal in that location almost like heat treating a small part of the shell making it uneven and warped. Also your creating a lot of stress on the seam because metal [even when rolled] still wants to spring back to it's original shape. This is sometimes a bad thing because the seam is brittle and could be susceptible to cracking. Shells created this way sometimes have harsh overtones and excessive ringing.
When an American Cast Shell is cast it is allowed to cool down to room temperature then it is sent off to heat treat, there it will be Solution Heat-treated and Artificially Aged. The process of Solution Heat-treating is done by heating the aluminum to 1000F for 4-12 hours and quenched in water at 150-212F, what this does is force the shell to cool evenly all around and all the way through, we harden our shells to a T-6 condition. Seamless shells not only look great when you polish, plate, or powder coat them they also have a superior sound to rolled shells.