I am going to attempt to reload for my 300 RUM. I have absolutely zero experience reloading so bare with me. I am going to start with my factory remington brass and the Hornady 212 ELDx. I am using the RCBS Gold Medal Die set and am currently hung up on what bushing I need. The instructions reference two different methods for determining the correct neck bushing however I get two drastically different values when I do this. When measuring a loaded cartridge I come up with Neck bushing of 0.336 - 0.337 When I measure using the neck wall thickness I come up with 0.343 ?? Clearly Im doing something wrong. Any input on what neck bushing to use with Factory Remington brass ?