SpudFiles

idk if this is a totally new concept but its new to me I thought it up last night and have been pondering it for many hours now and was wondering if anybody had any thoughts on if it would work or if not in theory why or why not thanks ahead of time here is the quick sketch I did

That's an interesting use of an air cylinder, but you really have the same effect from a QEV or a more common homemade piston valve. And as long as the air cylinder internal diameter is greater than the barrel diameter it should work fine.

But I don't really see an advantage to using an air cylinder over a normal piston valve design like the one I attached. Piston valves generally don't need to move more than 1/2" to get more than enough flow and savvy spudgun designers minimize the distance of piston travel and the volume of an that has to be vented to move the piston, this helps the piston to open as fast as possible.
On most air cylinders there's way more movement than necessary and way more volume of air to vent to activate the valve, more air to vent means it will open slower.

You can test which combination of piston valve dimensions work the best using the Gas Gun Design Tool GGDT which you can search for and download on this site.

i will give that valve you posted a try first thanks

I have built valves like this. Spring return works well too since ballast pressure will keep seal closed. They open nice and fast but it is true that you don't need much travel. They are also safer than a bleeding pilot type valve.

I see what you mean requiring positive pressure to open prevents the valve from opening every time you disconnect the air source, just need to machine more air seals.