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...
The Tippmann lines of guns houses the valve in a power tube that seals all the pressure in. If there is a crack in the tube internal gun leaks and start which will drop your gun performance! Be sure...
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...