You've missed the point of the design. The hole just needs to be more restrictive than the transfer port to start to make a difference. Let's keep it simple.....say the hole is the same size as the transfer port cylinder (more precisely, offering the same resistance to flow at a given pressure differential). Then, for the flow into the pot to be the same as the flow out of the pot, the differential between cylinder pressure and pot pressure has to be greater than the differential between pot pressure and barrel pressure. If the resistance to flow into the barrel is less than resistance to flow into the pot then the air pressure in the pot (and at the firing valve) will drop, restricting the flow out. Without the pot the pressure at firing valve remains (near enough) at cylinder pressure.RichieRich612 wrote: ↑Mon Sep 09, 2019 9:09 pmI think reducing or increasing the hole makes no difference at all.
The pressure within the cylinder at full charge is immense and would easily fill the plenum volume instantaneously regardless of hole diameter. We're talking tons of pressure here at 190 bar....
Another factor to take into account is that the plenum is just a way Air Arms have simply designed a way to adjust compression on the valve spring.
Therefore it's purpose is only to adjust the valve opening.
As the cylinder pressure drops the reduced pressure at the firing valve allows the valve to remain open longer, so the pot is counteracting this by reducing the pressure at the valve when cylinder pressure is high.
The overall effects are (a) to reduce air flow as the barrel pressure drops, reducing air wastage and improving air efficiency,) and (b) making air flow less dependent on cylinder pressure so the power curve is flatter.
You don't need a plenum "just to adjust compression on the valve spring". The pot assembly has two purposes: plenum and valve pre-load adjustment.