The BT4 Expansion chamber will add that extra look of milsim authenticity to your BT4 marker.

As well as looking stylish and authentic, the BT4 Magazine Expansion Chamber will help prevent liquid co2 getting into your marker's valve which can cause velocity spikes and poor gas efficiency. Expansion chambers help prevent this by giving the liquid co2 more room to expand - hence the name - helping to increase the consistency and the number of shots per tank.