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Old October 11, 2013, 08:53 AM   #10
Bart B.
Senior Member
Join Date: February 15, 2009
Posts: 6,318
Guffey, yes, firing pins do that.

But the last 1/8th inch of their tip has to be bent out 90 degrees from their long axis. Then placing it inside the case mouth such that it bears on the case shoulder .005" up from the case mouth diameter at that point. Then press with 17 pounds of force outward at evenly spaced points all the way around the inside of the case. The number of pressure points is pi (3.1416...) times the case mouth diameter in millimeters. A 30 caliber case would need 25 points (close enough for good accuracy) around it to form that donut on the outside of the shoulder.
US Navy Distinguished Marksman Badge 153
Former US Navy & Palma Rifle Team Member
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Last edited by Bart B.; October 11, 2013 at 05:28 PM.
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