In responce to the comment about your loading dies, 505 feel free to correct me!!! I think you will find out that the "505 Gibbs has a true diameter of .505" and the rifle shown is using the American diameter of .510" diameter for the barrel and bullet diameter. I have seen this with several .505 Gibbs built over here. Using .510" gives better bullet selection but causes a few problems with the dies. If you want you could probably fit your siving die with a .510" long tappered expander and solve those problems and get better accuracy with no other alteration to the die set.