Thanks Jack, I might put the schrader like that but in real life that will be quite small and I don't think the pump's hose will fit in that gap.
On the piston I might make it thicker on the outside so the piston wont flip because it's so thin. Making it thicker on the outside and making the sealing face stay thin it will add stability the the piston might even glide more smoothly.
One last question, it is possible to buy schrader valves from hardware stores just on their own? Or do I have to buy a whole bike inner tube each time and then cut the schrader off?
I am so excited to build this. Sadly, I have to wait until Christmas before I actually get my lathe and mill
Will be building a bolt action rifle, a Lever action shotgun and a pen-gun.
Thanks to everyone who has helped me!