"Yesterday afternoon I was converting my 550 from .223 to .38 to do a small batch in my living room. I had used my primer pick up tube to grab about fifty primers and had it in my left hand, placed it at the top of the 550 primer magazine, and with my right hand started to pull the pin. Kaboom!" http://www.calguns.net/calgunforum/showthread.php?t=495909 Primer dust can build up inside the tube. The tubes should be cleaned to remove this residue now & then. Not all primers are sealed with a coating.