Help please, 'eyebrows' after the range on .45 ACP brass?

[peppercorn]

I've been working up a nice target load for .45ACP and have noticed that some, not all, of my brass pieces end up with these, as pictured below, crescent shaped 'creases' after being fired.

The loads are medium to light HP-38 4.9-5.2 grains under a 200 grain Bayou SWC.

I am shooting these out of a SigSauer P220 and/or a Sig Sauer 1911.

I have not had any failures in any categories with any of the above loads.

My questions are,one, what is causing this and two, is it anything to be worried about?

 

[arjay]

If you're using a full power spring,the timings a bit off with a mild load and it's hitting the ejection port on it's way out.Mine get a bent case mouth from that,but it doesn't cause any problems resizing.I would guess it eventually weakens the brass,but I have so much I don't worry about it

 

[alde]

My Colt 01918 does that and worse. They reload fine.

 

[peppercorn]

Yes, my springs are stock. I'm glad it isn't something I was doing wrong.
Thanks for the great feedback, I really do appreciate it.

 

[smokindog]

http://smith-wessonforum.com/reloading/337058-another-45-acp-damaged-brass-question.html