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Old August 29th, 2009, 15:53   #2
GBB Whisperer
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Join Date: Jun 2002
Location: Toronto
I don't agree with your description of the NPAS versus PPS.

Both of them work on the same basic principle, in which gas is allowed to flow forward to project the BB, and once the BB moves, the valve then shuts off and 100% of all remaining gas is re-directed to fire the blowback mechanism. It's a 1-2 operation. The projectile always leaves the barrel first, before ANY type of semi-automatic self cocking action begins.
At no point is gas "split" to operate two functions at the same time. That would be inefficient and quite a waste of gas. Even real guns do not operate in this manner.

The difference in the systems, is what happens once the BB moves.

In the Positive Pressure System, the valve is CLOSED in its natural state, and requires a positive pressure against the nozzle in order to open the valve to allow gas to fire through the nozzle. In this case, the BB is the positive pressure, pushing the reed back in order to open the valve. Once gas is fired, gas is continually fired through until the BB is far enough down the barrel to allow the reed valve to naturally close (under spring power), which then redirects all gas power to the blowback cycle.

The Negative Pressure System alters this slightly, by allowing the valve to remain OPEN in its natural state. Gas is fired out of the nozzle to release the projectile, and continues to release gas until the BB clears the barrel. Once the BB clears, the pressure behind the valve builds to a higher amount than what's in front of the valve (in the barrel), and the result is the valve being forced shut. In essence, a negative pressure is built on the opposing side of the valve to cause it to operate. And again, once the valve is closed, all gas pressure is redirected in to the blowback cycle of the operation.

*Most* modern GBB pistols operate through this "negative pressure" concept, with WA being the exception (which is no surprise why this Magna system was based on such a design.)

Last edited by ILLusion; August 29th, 2009 at 15:58..
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