Newbie needing help


Apr 17, 2017
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 ?


Well-Known Member
May 12, 2016
What is the neck wall thickness measurement you are getting?

.343 does sound bigger than it should be. I believe most neck thicknesses are around .012-.015 so using a .308 bullet would put you around .332-.338 actual size so pick a bushing .002 smaller.

Measure just the neck wall (not diameter) of your fired brass in a few spots around the mouth on a few cases and take the average. Any case that varies more than .002 from the rest set aside till you learn to neck turn.


Well-Known Member
LRH Team Member
Sep 24, 2016
Frankfort, Ky
Yep....what Lonewolf74 said. Here's one way that I measure neck thickness in order to determine loaded round diameter. I'll use a vernier ball micrometer and take a reading of neck wall thickness of several cases. Get the average of those readings and multiply that figure by 2 and then add my bullet diameter to that figure which results in the loaded round diameter. Then I'll order a bushing .001-.003 less for proper neck tension. You could always get some sort of Concentricity Gauge (you'll want one eventually) and use it to determine neck thickness if it has the capability. Just follow the same formula....multiply the initial reading by 2 and then add bullet diameter to get the loaded round diameter. I have a Forster CoAx Case Inspector and it is spot on in agreement with a vernier micrometer.