Bob, how fast were you pushing these pin loads?
I push my pin loads as hard as I can safely go, so as to knock the pins off the table.....
Berry's advises no faster than 1200, IIRC.
I will agree that oversized bullets=pressure spikes. Hot loads make that worse.
Did you call Berry's on it? I'm sure they would have been very interested in any QC problems they might have had.
TheGolden Rule of Tool Use: "If you don't know what you are doing, DON'T."