The Tippmann FT-12 uses a unique barrel nut that allows the marker flip open! Over a period of time the plastic can get worn out or cracked if over tighten. Replace the part or your gun might flip...
One of the benefits of the Tippmann FT-12 is that it doesn't have a gas line hose. The gas line can eventually break and leak on you so it's best to be sure you have one just in case in your gear...