OK, I have a couple of dummy rounds that I cannot pin down. I placed a 20x102mm next to them for comparison. The one is one-piece solid brass. The "case" is 4.79 inches long with a rim diameter of.98 inch and a neck diameter of .815 inch. The visible "projectile" is 2.05 inches long and .81 inch in diameter. You will note there is no rotating band on the projectile. They went to a lot of trouble on the base to form it the way they did instead of a plain flat base. The second round is very heavy. It has "case" that is 3.78 inches long with a rim diameter of 1.48 inches and a neck diameter of 1.13 inches. The exposed "projectile" is 3.14 inches long and 1.13 inches in diameter. The main round is solid one-piece and I'm not sure what it is made out of. It is not magnetic, bright and shiny. Could be stainless steel with a high nickel content??? There is a brass sleeve fit over the lower portion to simulate the cartridge case. Again, someone spent a lot of time putting this one together. Anyone else have one or know what they are??