The fault is with the needle valve, not the single stage regulator.
What needle valve do you use (Or are you using a flow control valve) I have been using single stage regulators for the past 14 years. Have no problem with Co2 getting dumped at the end. I am able to get proper use of the CO2 until pressure falls to 300 PSI in the Co2 tank, then I get a refill.
Why not just run it empty? Oh right gas flow increases..
That btw is pretty much undeniable physics except w/ some better designed 1 stages..
The single-stage regulator shows little droop with varying flow rates, but a relatively large supply pressure effect. Conversely, the two-stage regulator shows a considerable droop, but only small supply pressure effects. Generally, a single-stage regulator is recommended where inlet pressure does not vary greatly or where periodic readjustment of delivery pressure does not present a problem. A two-stage regulator, however, provides constant delivery pressure with no need for periodic readjustment.
What is Supply Pressure Effect (SPE)?
Supply pressure effect, also referred to as inlet dependency, is defined as the change in outlet pressure due to a change in inlet, or supply, pressure. Under this phenomenon, inlet and outlet pressure changes are inversely proportional to each other. If the inlet pressure decreases, there will be a corresponding outlet pressure increase. Conversely, if the inlet pressure increases, the outlet pressure decreases.
A regulator’s supply pressure effect is typically provided by the manufacturer. SPE is usually depicted as a ratio or percentage describing the change in outlet pressure per change in inlet pressure. For example, if a regulator is described as having a 1:100 or 1% SPE, for every 100 psi drop in inlet pressure, the outlet pressure will increase by 1 psi. The degree of outlet pressure variation for a regulator can be estimated with the following formula:
∆P (outlet) = ∆P (inlet) x SPE
What it implies is determined by how close to death you are running your CO2..
Don't rule out that the changing pressure may effect your metering valve.
In that case it would be "chicken or egg"..
With a regulator controlling outlet pressure from a gas cylinder, SPE is a phenomenon that's always at play. Whenever inlet pressure changes, outlet pressure also will change. It's only noticeable — or only becomes an issue — in certain situations, for example, when regulation of the outlet pressure must be very precise or when inlet pressure has changed significantly, such as when a gas cylinder is emptying. You can minimize the effects of SPE for many applications by using a single regulator with a balanced poppet design or a two-stage regulator.