It looks too low for the edge of the loading die to catch it at the taper crimp stage. This assuming you have taper crimp dies. Its worth checking though.
I clean the inside of my PW dies fairy often, quick wipe starting a session, they will get dirty inside and cause sticky ejection and vertical score lines on AA hulls. Never seen horizontal lines
Primary diagnosis trick does it repeat, that would indicate press problem. Random its the hull
** missed the pump gun part, adds another variable, check the carrier for sharp edges, paint a fresh hull with black marker cycle & see where the carrier is hitting the hull. Could be edge of the loading port too. Don't know about m37 but new 870 pumps have very sharp edges. Sharp enough to be hard on fingers, had to de-burr one for my son.
William
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