Boneguru,
Sorry for the dumb question. I didn't read it very well or I would have seen the Glock in your post. Unsupported case heads in the Glock chambers have been a problem in the high pressure .40. I'd watch the case heads closely for signs of fatigue. If the case head bulge is bad enough you have to have sizing dies milled to resize the bulge away, you are close to case head failure. If this is happening with factory ammo, I'd send the barrel back to Glock for inspection. If it's just with your reloads, it's time to take a critical look at your loads.
Stay Safe,
Savage