False. Not sure what else to say here, that's just not how gas works. For all practical purposes CO2 is instantaneously 600psi at room temp, whether the valve is open for a millisecond or 10 seconds. How long the valve is open simply determines how much gas comes out at 600psi. Excess pressure must be blown off.
Why does the PSI matter so much? The important thing here is the volume of gas released.
Let's see if we can agree on one thing first so we're on the same page.
Let's say you have a stock Green Gas magazine and your gun shoots about 300FPS, and gets 30 shots from a fully charged mag. If you install a high-flow valve, you get higher FPS, more energy to cycle the gun (which may be too much and wear your gun out faster if you didn't get a reinforced slide) but use more gas per shot so run out faster. This is because the more free flowing valve releases a bigger volume of gas per shot. The pressure of the gas remains the same since you're still using Green Gas, the only thing changing is the volume released. You are basically trading more power for less shots. True?
If so, then the opposite must be true. Releasing a smaller volume of gas using a more restrictive valve that opens less and stays open for a shorter period of time will decrease your muzzle velocity (with GG it would probably be down to pretty useless levels, with CO2 it would be down to about what you get with GG from a stock valve, depending on how much you want to restrict), decrease the energy of your gun's action cycling (thus saving on wear and tear), but allow you to fire more shots before running out.
If that is true then it should be true regardless of if you are using Green Gas/Propane or CO2. The only difference being that you would use overall more restrictive valves with CO2 than with Green Gas in order to achieve the same muzzle velocity and blowback force. Since you are restricting how much CO2 is released in order to get safe velocities, then you get the added benefit of using less gas and thus getting more shots per mag. I don't see why the extra gas would be lost or blown off as you say if it never leaves the magazine in the first place.
The way you say it makes it seem that installing a high-flow valve on a GBB would not change your velocity since the gas you use is still the same pressure. You would just be dumping extra gas for absolutely no benefit or change in performance except that you would run out faster.
1. That magazine has a static regulator, probably made from a series of o-rings that bottleneck the pressure. Probably regulating down to ~120psi. It's not about hammer springs and firing pins or anything like that, it's about regulating the output pressure.
2. The magazine was near freezing (I think it said 9C). At room temp it would have a much higher velocity.
1. That's exactly what I'm trying to say. Using a more restrictive flow valve on your magazine (like a low-flow, do they even make those?) Would regulate the CO2 pressure down to safe levels and leave the extra gas in the mag for the next shots. Perhaps the weaker hammer spring idea was off, since this would work better with a more restrictive flow-valve instead. But the idea is the same. Release less gas per shot.
2. Both the Stock mag and the CO2 mag were in cold water and taken out about the same time. Since the GG mag shot 322 FPS, which is what you would expect from GG at about room temperature. I think it's safe to assume the CO2 mag was also about room temperature by the time the velocity test was done.
It still suffers from cooldown, although not as drastically. Instead of being unable to finish a mag, your velocity will fluctuate because it only has a single, static regulator. It's an improvement on gas magazine designs, but not the improvement that needs to be made.
What regulator? You would just be using a more restrictive valve. There is no regulator per-se and nothing extra that needs to be crammed into the mag. No costly R&D and no real change in the design. This has been done before. They make high-flow valves. They can make a low-flow just the same. In fact the thing I will test is that I can make a standard valve from my GHK AK CO2 mag into a low flow by putting a small brass ring into it around where the spring is that will prevent the valve from opening all the way.
You couldn't do it with a single-stack 1911 mag
$30. Make the valve on it more restrictive and you're golden.
As far as compacts. I think it's a fair price to pay for better performance. Not many players use compacts to skirmish. Most use a full size service pistol of some sort. P226, 1911, G17, M9, USP all of those can take CO2 mags just fine. Most have a kind of ugly looking block thing on the bottom for the screw. But WE even fixed that with their CO2 M9 mags which have the same floor plate as a regular mag. So that's not even an issue, as small an issue as it would be. If you just like compacts to collect and plink with, then performance is not really of utmost importance, so you can stick with Propane mags. But why should full size pistols be restrained by the limitations of a compact when they can easily be way better.
The reason GG is still the rule is cost.
At 129 shots per 50c CO2 capsule. I don't think the cost will be all that different. Many might buy them if it means not having parents/significant others complain about the stink of Propane (which is the only way Green Gas mags are anywhere near cost effective) everytime you shoot your gun. It's a bit of a problem to me. While I'm completely used to the smell and don't notice it. It still means that I can only shoot when NOONE else is home and every time I want to show off my new toy to some friends they all say "Yea I'd rather not". Shooting outdoors is not really an option around here.