You should sand/taper the cut end of the pipe, if not it will have a slight flare on the end and act like a squeegee when you push it into the fitting which could result in a faulty joint that will no doubt let loose at the worst possible time.Sheesh - I feel bad. Not only do I use primer but I also sand each fitting to rough it up. I treat it just like I'm throwing sprinklers in the yard - go figure.