The trick behind that semi-pistol is that he just needs to used his hand as a biological railgun where his thumb and forefinger acting as both focusing lens and trigger.
Between his fingers, his body's micro-tremor network compressed ambient air molecules using high-frequency vibrations.
The narrow space between his fingers functioned as a containment zone, where oscillating kinetic energy was layered into the air creating some kind of a pocket of extreme pressure without combustion or heat.
This is possible because his Kinetic Vein Art can now channel direct vibration energy into external air through his fingertips, turning them into emitters.
Through that static conversion, his kinetic energy partially ionized the compressed pocket of air at his fingertip.
This reduced the resistance and allowed him to store pure motion as potential energy in a window so short it was almost impossible to measure.
