The tips on the big soldering guns are infamous for opening at the end. It usually happens when you are out at the edge of nowhere and far from a hardware store. No worries, mate!
Strip off a five or six inch piece of AWG #14 solid copper wire out of a piece of Romex(tm) or similar house wiring, bend it to shape with your pliers, stick it in the business end, tin it, and you are back in operation.
Wait! You have the tip upside-down!(You exclaim).
No I don't (I respond). Take a look at where the little light on the gun shines. Putting the tip down in that area makes more sense, right? It doesn't quite fit the image of the barrel of a pistol that way, though. I suppose that is a selling point for the design of the tool. Remember the old Wen(tm) Model 75 soldering pistol? It even had the "cylinder” indentations for the bullets. A pair of chaps, a neck bandana, and a white cowboy hat would make the outfit complete, eh?