hey guys almost ready to reload my first set of 9mm rounds. Final question (maybe), in my reloading book it said NEVER crimp 9mm rounds. However I saw online (youtube reloading video) that some do crimp their 9mm rounds. My question is, is it better to not crimp and follow the book or does crimping provide something more sufficient that the book does not discuss. I will be shooting these reloads out of my glock 19 as well in case that plays any special part in it. Thanks in advance