The gun is a Glock 17 gen. 2. Today I got 1000rnds of 124 grain L7a1 ammo. I shot 4 rounds and all four have a flat spot on the ejected case and a small scuff at the flat point. I also ran some S.A. 9mm 115grn thru the same gun in the same mag right after the Hirt. and none of the S.A. have any flat spot they are all perfectly round. Does anyone know why the Hirt. deforms the case.

Try a different lot of 9mm NATO (124gr).  Comparing to 115gr won't tell you much.  Case is striking the pistol on the way out probably.  As long as the pistol functions well I'd not worry about it.

-- Chuck

I have a Glock 31 in 357 Sig, and it did the same thing. I solved the problem by putting a heavier poundage recoil spring in it. My guess is that the new spring decreased the speed of the slide,so the cases are not getting slammed into the edge of the ejection port. I have heard that the Hirtenberger 124 gr. ammo is sub-gun ammo, and loaded very hot. If you are not concerned with the appearance of the fired cases, don't sweat it. But a heavier spring may ease the battering that your pistol is going to take with this stuff.