The above image shows the slow speed, low pressure phase of the bolt stroke. It is very slow - about 4-6 FPS (as compared to 20 FPS for the Level 7 valve). This slow speed and low pressure makes sure the bolt will pinch rather than chop a paintball. There is an additional advantage - the slow moving bolt does not crack or bobble the ball waiting to go in.
A smaller diameter (as compared to the level 7) power piston gives the pressurized air within the chamber less area to push against. This, combined with a stronger bolt mainspring gives us the slow initial bolt force & acceleration.
As the bolt starts its initial travel, the small vent hole in the power piston moves past the power tube o-ring. As it does so, the hole begins to vent a small amount of air which leaks out through the power tube tip, as shown in the image below. The amount of air venting is miniscule and has a very minor effect upon gas efficiency.
Why do we have the vent? If a paintball is partially in the breech, the slow moving bolt will stop on the ball, rather than chopping through it. When the bolt stops on the partially fed paintball, the power piston vent allows the pressurized gas in the air chamber to escape. Once enough air pressure escapes, the bolt spring pushes the bolt back and recocks the marker. Also at this time, the paintball drops the rest of the way into the breech and the marker is set to fire once again.
Above we show the second stage of bolt acceleration which starts after the bolt gets past the ball stack. During this acceleration stage, the end of the power piston moves completely past the power tube o-ring. This allows pressurized air to flow into the power tube where it pushes against the larger diameter section in the middle of the power piston. At this point, the bolt accelerates to full speed - approximately 15 FPS. It is at this point where the valve goes to full power - loading the paintball into the barrel, firing, and retracting the bolt.
This second acceleration stage is very important - it allows us to maintain the high firing rate of the marker. If the bolt continued to travel at the same speed it would severely limit the firing rate. The animation at the top does not properly show the speed increase.
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