Alright, if you can't grasp this concept, then you are (in essence) a "stupid ****ing idiot".
When a 180psi enters into the chamber with volume x, the gun is charged at 180psi. The input to the dump chamber seals off when the bolt moves forward containing 180psi at volume x. When the transfer port opens up, the chamber AND the bolt face are pressurized. If the bolt face has volume y, then the new pressurized area has a volume of x + y. Since x + y is naturally a higher volume than just x, the pressure inside the marker behind the ball will decrease with the larger volume. Thus you get an input pressure of 180psi and a firing pressure of 45 psi.