Any swager that supports the case from the inside is dependent on case web thickness for uniformity. Consider these three sectioned cases -



If these are swaged with the same adjustment, all would show different results because of the differences in web thickness (and contour). In addition, the presence of any significant inside burrs (as on the R-P case here) will have a small effect on the swaging action (and possibly a major effect on the flash hole opening if the burr is mashed by the support rod).

Uniform results occur with uniform conditions, best assured by processing cases of the same production lot together and inside-deburring flash holes before swaging. Re-adjustment of the tool is often necessary to maintain uniform pocket swaging when a different brand or lot of cases is processed. If case lots are mixed or unknown, or cases exhibit poor uniformity within a single lot, pre-sorting by weight may help (and may also enhance accuracy).