I used the rim diameter + diameter of the bottom round at that point to calculate proper width of 24 mm. I stopped removing material at 23 mm or there about because the round no longer sprung back and chambered every time for 100 + tests. What is interesting is that the article said that Mauser relieved his magazine boxes in the middle to reduce friction but I think that it may have been to solve this very problem. As the rim slides down, it is much wider than the cartridge and so needs about 1 mm extra width just as it reaches the chamber. The 458 win mag seems to be a perfect storm where a Lott will probably be fine because it is longer and has less steep angles as it feeds. Much thanks to Von Gruff and TokkieM for their answers to my Pm's
