I was taking apart my new Gen 4 G21 and I noticed a little notch on the upper right corner of the very bottom of the channel. However I can't see if it is by design, or a piece of debris. I don't recall seeing this in my Gen 3 G19. My understanding is that the firing pin channel is the one part of the Glock that should really be kept clean. (I keep everything clean, though.) Can anyone offer any insight? Thanks a lot. That little tiny notch all the way at the bottom on the top right corner. Here is another: Thanks everyone!