A fastener driving apparatus comprises a gas spring or spring, a drive mechanism, an anvil assembly, and an anvil. The drive mechanism permits transition from engagement with the gas spring, spring or anvil assembly to disengagement from the gas spring, spring or anvil assembly. The anvil and/or anvil assembly are operatively coupled to the gas spring or spring such that after the drive mechanism disengages them, the gas spring piston or the spring moves to imparts a force on the anvil to cause the anvil to move and drive a fastener. The mass of the anvil assembly is preferably greater than 50% of the total mass of the anvil assembly and gas spring moving mass. The gas spring is configured such that the pressure increase during the movement of the gas spring piston by the drive mechanism is less than 30% of the initial pressure in the gas spring.