I might be able to solve the issue with the power dropping as the hammer screw adjustment is shortened. Behind the lock screw for the hammer screw is a vent hole. It allows air to flow through the hammer to prevent a vacuum behind the hammer when fired. (If you will notice, there is a hole through the spring guide/top hat.) Shortening the screw protrusion gives more power, but at a certain point, the back of the adjustment screw will start blocking the vent hole. This can start causing a vacuum behind the hammer and will prevent the hammer from getting a full strike on the valve.
The quickest fix is to remove the safety. With the safety screw gone, the hammer can breathe through the screw hole and eliminate the vacuum. If the safety is a necessity, drilling a vent hole through the rear cap will allow the hammer to breathe
Wet lube on the hammer will cause the same effect. The air moving around the hammer is impeded by the lube and the vent through the hammer can't provide enough flow for free movement of the hammer.
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