Quote:
Originally Posted by Retired LTC, USAR
My Father used to reload and hopefully one day I will be able to get back into it, but I do have one question.
What is the difference between a roll crimp and a taper crimp?
Pictures would be helpfull if they readily show the difference.
Thanks.
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Sir, if you have them handy, get out a straight-wall auto pistol cartridge (.45 ACP, 9 mm, etc.) and a revolver cartridge (.357, .44, etc.) and compare the case mouths. The revolver cartridge's case mouth will be pinched (crimped) into the cannelure of the bullet; this is a roll crimp. The auto cartridge's case mouth will be "straight" and not pinched into the bullet; this is a taper crimp.
Auto handgun cartridges use a taper crimp because they typically headspace on the case mouth. Revolver cartridges headspace on the rim, so the exact location of the case mouth is less critical than it is in autos. A taper crimp is basically a friction fit, like clamping something in a smooth-jawed vise. A roll crimp is more of a mechanical lock, which is good with magnum loads.
Hope this helps, and Semper Fi.
Ron H.