One of the worst things that could happen during a IPSC match or a regular airsoft game is your loading nozzle breaking half way or even before it starts. Dynamic Precision has produced a aluminium loading nozzle with a for the Tokyo Marui Model 18C GBB Pistol. It will even allow you to use red gas so long as your other internals can withstand the pressure.
Disclaimer: All aftermarket upgrade parts require necessary skill or modification to install and assemble, please consult with your airsoft technician if needed.