A well tool comprising an upper sub having: a housing that includes a first chamber for receiving an igniter, the igniter generating a flame output when detonated, a pressure sub having: - a cylinder having an inner surface defining a bore, the cylinder bore having: - a smooth bore section defined by an inner surface that is dimensionally non-varying both circumferentially and axially, and - a pressure chamber that generates the pressure needed to displace the cylinder in a direction away from the upper sub, and - a shaft disposed in the cylinder bore, the shaft having a bore, a first end connected to the upper sub, and a second end on which a piston assembly is formed, the piston assembly including at least one seal contacting the inner surface of the cylinder, - a power charge disposed in the shaft bore, the power charge characterized by: the power charge being formed of an energetic material that generates a high pressure gas when ignited by the flame output of the igniter, said high pressure gas flowing into the pressure chamber, and - a pressure dissipater formed at a terminal end of the cylinder, the pressure dissipater contacting and physically destabilizing the at least one seal after the at least one seal exits the smooth bore section, whereby gas leaks past the seals and the pressure in the pressure chamber drops; and a lower sub connected to the cylinder and configured to axially displace a component of a separate wellbore device. a housing that includes a first chamber for receiving an igniter, the igniter generating a flame output when detonated, a pressure sub having: - a cylinder having an inner surface defining a bore, the cylinder bore having: - a smooth bore section defined by an inner surface that is dimensionally non-varying both circumferentially and axially, and - a pressure chamber that generates the pressure needed to displace the cylinder in a direction away from the upper sub, and - a shaft disposed in the cylinder bore, the shaft having a bore, a first end connected to the upper sub, and a second end on which a piston assembly is formed, the piston assembly including at least one seal contacting the inner surface of the cylinder, - a power charge disposed in the shaft bore, the power charge characterized by: the power charge being formed of an energetic material that generates a high pressure gas when ignited by the flame output of the igniter, said high pressure gas flowing into the pressure chamber, and - a pressure dissipater formed at a terminal end of the cylinder, the pressure dissipater contacting and physically destabilizing the at least one seal after the at least one seal exits the smooth bore section, whereby gas leaks past the seals and the pressure in the pressure chamber drops; and - a cylinder having an inner surface defining a bore, the cylinder bore having: - a smooth bore section defined by an inner surface that is dimensionally non-varying both circumferentially and axially, and - a pressure chamber that generates the pressure needed to displace the cylinder in a direction away from the upper sub, and - a smooth bore section defined by an inner surface that is dimensionally non-varying both circumferentially and axially, and - a pressure chamber that generates the pressure needed to displace the cylinder in a direction away from the upper sub, and - a shaft disposed in the cylinder bore, the shaft having a bore, a first end connected to the upper sub, and a second end on which a piston assembly is formed, the piston assembly including at least one seal contacting the inner surface of the cylinder, - a power charge disposed in the shaft bore, the power charge characterized by: the power charge being formed of an energetic material that generates a high pressure gas when ignited by the flame output of the igniter, said high pressure gas flowing into the pressure chamber, and - a pressure dissipater formed at a terminal end of the cylinder, the pressure dissipater contacting and physically destabilizing the at least one seal after the at least one seal exits the smooth bore section, whereby gas leaks past the seals and the pressure in the pressure chamber drops; and a lower sub connected to the cylinder and configured to axially displace a component of a separate wellbore device.