Runout and Reloading Dies

Reloaders like to measure runout.

If you are one of them, then you have invested in equipment to check loaded round concentricity.

What you are measuring ? Is the runout you are seeing what you think it is ?

Break the concept down into it's componenets and think about them for a minute.

Runout is the measured deviation of the case neck axis from the case body axis.

When deviation is present, there are a limited number of factors able to cause it :

  • the decapping rod assembly
  • the seating stem
  • neck wall uniformity
  • brass hardness and springback

Factors that have nothing to do with runout are

  • the press
  • the sizing die body