I bought a new Glock 19 Gen 4 a couple weeks ago and it jammed 4 times on the first two clips. I called Glock and was told that I have the correct spring, so I did a lot of internet searching to see if anyone had the same problem. Ran across one video where they suggested cleaning out the copper grease on the slide. The theory is the grease is so thick that it prevents the slide from going all of the way back and it then does not allow the next round to feed into the barrel before the slide comes forward. I removed the copper grease, lubed it with a coating of oil and took it to the firing range. Fired 150 rounds without a single problem, No more ejection problems and no more jamming problems.