I purchased a G19 Gen4 in OD, and I started researching the changes from Gen3 to Gen4 and I happen to notice that the front of the slide around the hole for the recoil spring looks very thin and delicate compared to the Gen3. It's thinner on the Gen4 because the recoil spring is wider so the gun needs a larger hole. I have seen pictures of high mileage Glocks and there is sometimes a crack around the recoil spring hole even on the Gen3, but then again we are talking about 200,000 round Glocks. Am I worrying over nothing? On another note, the metal around the recoil spring on my HK45c is built like a tank.