[Stahl]

Sometimes a case will develop a "wrinkle" after a few loadings. It happens about .200 from the end of the casehead (.40SW). Does anyone know what this is and what causes it? Is it safe to reload a case that has developed this?

[Grump]

.20 from the casehead could be the unsupported case wall getting ready to let go. They are usually curved. Is there a corresponding crease or thin spot on the inside opposite your "wrinkle?" If so, TOSS 'EM. That would sound like an incipient head separation, very bad.:uhoh:

Any way to post a pic?

.20 from the case mouth would just be bullet seat/crimp fatigue. Generally not dangerous in my experience, but still reason to toss them.

[HSMITH]

Sounds like the brass is bulged and you are ironing the bulge out, this will wrinkle eventually when the brass is stretched and gets hardened to the point that it will not size back normally. This has happened to me with high pressure loads fired in stock Glock barrels 6 or 8 times, but nowhere else.

What are the circumstances that lead you to this problem? Brass fired X times, load data, gun type, etc.

40 brass is nearly free. If it even begins to look a tad bit off heave it and get some more. There is no reason to chance anything with brass that costs less than two cents each for once fired brass. Jump on ebay and grab a couple thousand cases, you can often get them to your door for less than $20 per thousand.