Illustrated is an excellent example of slovenly equipment upkeep that can affect accuracy. These "shoulder dents" are not the result of excess lube. You can see the dent is "squared" and on the same spot on each cartridge. I managed to resize and load 35pcs of brass before noticiing something was wrong. Because the dent spanned the shoulder-case, chambering was difficult ...and accuracy suffered. Issue resolved by cleaning the sizer die. Firing the cartridge blows the dent back out.
I usually clean at about 400 - 500 reloads...or whenever I change lube types. The issue shown in the pic was likely the result of "a piece of something" comming off a case and sticking in the die. This one could have been a flake of carbon. It must have been pretty thick, as the die is a neck sizer only.
It is also a good idea to frequently clean the shellholder in the ram as it can get dirty enough so cases get crowded to one side which can potentially affect concentricity.
Cleaning Resizing Dies
Linear Mode
