I had a conversion barrel from Storm Lake to take a Glock 21 to Glock 20. The zero didn't change on that one, and it shot very well. It would eject reliably, but all over the place. My theory was that the larger slot cut in the slide to fit the 45ACP case head was allowing the 10mm case to move a bit and hitting the ejector in slightly different spots. After trying several different extractors, I gave up on it. It never failed to eject, but I got tired of chasing 10mm brass all over the landscape, sold the conversion barrel and bought a G20.