The theory of how you could get an overcharge of powder in a progressive loader goes like this, 1st powder charge drops but gets hung up in the tube, second charge drops and clears 1st and second charge drop into shell. When loading light loads the wad often has a short shot cup and a long cushion area. It is part of the theory that this cushion area collapses and makes room for the over load of powder.

You can never know for sure about these things after the fact. But I know 2 long time reloaders using progressive loaders that blow up chambers. Both dissected other shells from the session and found light or missing charges. One loaded up a double charge to test the theory. it pressure tested over 30,000psi.

Mark

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