You can shorten the lfe of a case if you fatigue the metal by setting the die too low for spreading the mouth. I made tha mistake when I first got started. This visible signs are slight imperfections in the mouth of the case. These lead to cracks and splits.
Particularly on straight cases lke 9mm, 45ACP and 38/357.I Clean and polish my cases well. My old eyes need all the help they can get. The cleanliness seems to expose the flaws I spoke of...........
