Introduction: Homemade 400 Psi Airgun

About: 17 Years old, doing a Masters in Professional Engineering (chemistry/mechanical) starting at UWA next year. I like designing and building things, as well as competitive archery

15.5 mm Bore, 1:30 helical cut rifling, aluminum, brass and stainless construction.. Calculated at mach 1.2 with hydrogen at 400 psi. Main ammunition are marbles..

Barrel: 15.5mm x 1.2m, 1:30 rifling (ammo; wadded marbles)
Chamber: 15.5mm x 80cm
Operating pressure: 120-400 psi
Blowgun porting, male QD for filling, with a built in internal check valve
Semi-bullpup configuration

I made a hand pump for it, which will easily reach 400+ psi, but takes far too long to bring the gun to pressure. So I'm going to buy a 260 psi track pump and use that..

Any questions? By the way I'm going to make a nice handle for it..