I bought two Gen 4 Glock 19s in 2012, one new and one slightly used. Both have peppered my face with hot empties since the first magazine in each. It hasn't been a random erratic ejection but, 2-3 empties out of every magazine. My wife would laugh when I came in from the range and took a close up photo of my face one day since it had so many black marks on it. I had tired several of the fixes suggested by members of this forum with no improvement whatsoever. Both guns have the most up-to-date Glock parts so I decided to try the APEX Glock Failure Resistant Extractor in one of these guns before giving up. The APEX extractor isn't a cheap part with total cost of the part and shipping coming to $68.00.
I installed the part and took it to the range yesterday with a mix of ammunition brands and loads. I started firing and had no brass to the face with the first magazine, which was the only time I had made it through a full magazine from either of these two G19s without at least one hot empty to the face. The second, third and all other magazines emptied with the same result. The empties ejected to the right just as they should and I had a clean face for the first time I had shot this Gen 4 G19. In all I fired 175 rounds with not a single BTF and I am well pleased with this APEX extractor. This afternoon I'll order another one for my second Glock 19.
I have owned several Glocks in the past and never had this problem with any of them, or any other handgun for that matter. It has been confined to these two Gen 4 Model 19s. If you are one of the unlucky few who have a Glock 19 which exhibits brass to face behavior you might try the APEX extractor. It seems to have fixed it for this one G19 of mine. I'll run a couple hundred more rounds through it next week as a follow-up.