A pneumatic fastener driving tool that forces pressurized gas from a gas supply source into a chamber above a piston enclosed in a working cylinder. During an operational cycle, the pressurized gas is released, forcing the piston to fire. The firing valve seals the pressurized gas utilizing two rolling diaphragm seals, thereby providing less breakdown of hardware and removing the need for lubricant within the firing valve. These diaphragm seals exhibit a smaller diameter than prior diaphragms used in similar pneumatic fastener driving tools.