Situation: Filling FX Crown. Event: User error - although the user always checks/tugs on the Foster connector to make sure it is seated and locked, this one blew off at ~200 bar pressure. What made things worse - Crown's pressure gauge is read from the bottom of the stock, right next to where Foster connection is made and user was watching the gauge during the fill process (at the time user was using a compressor which did not have an auto shut-off when a specific pressure was reached). Result: User took one between the eyes. This photo was taken after the bleeding was controlled through direct pressure. Lots of blood vessels in one's head - head wounds bleed a lot. I should have taken a photo of the gun on the garage floor covered in blood, but for some reason I wasn't thinking straight at the time.
Since this event:
1) Fill whip is always pointing away from me when filling, even though I have checked and double-checked the connection.
2) I added a better (digital) gauge to that compressor, so now I read fill pressure off of that instead of off the gun.
3) I have placed a shelf next to my compressor so I can fill the guns while resting on the shelf, and not holding the gun or with it resting on my lap.
4) Others have also suggested that the fill whip end can be tethered using either a rope or elastic cord to limit its travel in the case of high pressure disconnection.
I have also read of at least one incident (cannot verify validity, but there were photos) of certain high pressure air accessories which let go at pressure. This was an extra air supply for a gun which had a really small OEM air cylinder, and was being made and sold by "one of the guys on the forum." (This was NOT the AGN forum) Did a number on the gun, but apparently (fortunately) not on the user. I only use pressure vessels with DOT or ISO certification.
I have had burst disks go on one compressor, and some guns also have them. I had not exceeded that compressor's maximum working pressure, but burst disks are continually being flexed on every fill, and eventually weaken and let go. Fortunately I knew what happened (I used to work in a SCUBA shop many, many moons ago, so I have been around plenty of bursting burst disks) but my buddy just about jumped out of his skin.