ive shot it at least 25 times now at 100 psi... no leaks, no failures, i shot a 6" nail at a 1" thick board and split it.

not sure what you mean by frontal seal ant... the only seal it has is a circle of innertube glued to it to seal the barrel... and vh_man the lip wasnt intentional. it just happened the way i made it and i decided not to cut it off. this way the piston only has to move like an inch and doesn't smack ...

im guessing you are using a bike pump to blow it up... if you have an air compressor use it and it will probably have the pressure to seal it. my gun doesnt seal right untill i get 40 psi in it...

kindof a bummer i know...

I dont think it is going to wear off (it is actually thicker than my quick drawing) but ill keep that in mind. the glue i used is more rubbery than normal hot glue too

I also glued a piece of rubber innertube to the top to make a better seal

I looked at a lot of designs and found piston valves to be very complex (i have only before built basic combustion or ball valve pneumatic guns) i thought it would be easier to just make my own piston out of hot glue. I using a piece of 1.5" pipe as a mold i made a piston to fit. i set the 1.5" pipe...

Just use a bigger pilot valve. i couldnt get mine to fire until i used a ball valve.