what's the advantage to replacing the stock spring? You can use the springs to fine tune your velocity. Essentially, the velocity adjustment screw simply creates disturbance in the air flow that is released from the valve forward past the velocity screw. The screw disrupts the airflow increasing or decreasing the velocity of the air, thus increasing/decreasing the velocity of the paint. The amount/duration of air leaving the valve is controlled by how hard the hammer hits the valve pin. The harder it hits the pin, the more and longer the valve stays open, thus the more air is released from the opposite side, thus changing the airflow out the other end. Obviously, decreasing the pressure on the pin will decrease the amount of air out. So by using a harder or softer spring, you can theoretically fine tune the amount of air released and have less need for using the velocity screw. Less air released, greater efficiency. You can also use this in conjunction with a Rear Velocity Adjuster that replaces the stop back cap on the 98. This will allow you to essentially screw the velocity screw out so that it does not protrude into the airflow. You then use the RVA to adjust your velocity by increasing or decreasing the pressure on the spring.

why so many choices?

doesn't the existing velocity adjuster work just fine?

 

a stiffer spring will cause the hammer to hit the valve pin harder, releasing more air, thus increasing the velocity? Yes. And a softer spring will do just the opposite.

 

btw, i'm running compressed air and a cyclone feed only (no RT). any recomendations on which spring to use, or simply stick with stock? i mean, the gun fired great stock and i've never had a problem with the current gas consumption. Each set up is different. Trial and error is really the only way to be sure.