There are many threads on the net about this issue especially especially with 9mm. Most attribute it to the brass being too clean. I dry tumble with walnut and still occasionally have the issue. I've found using One Shot case lube almost always resolves the sticking. I put my 9mm brass in a zip lock bag add a blast of One Shot, zip and tumble. Works great! I have a 550b with Dillon carbide dies and One Shot just makes everything run that much smoother.