Air Pressure and Ball Valves
NO , a ball valve only will control flow. If you even allow a slight orifice the size of a human hair with time the chamber pressure would be at 800 psi. 

I would look for a used scuba regulator they can handle up to 3000 psi and the first stage around 135psi , their actual output pressure can be adjusted a little. 
I mention this because I used an old scuba regulator to charge my potato guns. 
Other possible regulators C02  I think they are 1200psi with the output being adjustable, oxygen or acetylene regs, 
Try Craig’s list or eBay for used regs possibly from a welding shop call and ask. 
There are lots of options that will be much safer.

Do not use a valve you need some kind of regulator.