They're meant to be a one time assembly, not disassembled and reassembled multiple times. Although I've been known to violate that rule on more than a couple of occasions
I've heard that "gauge block is regulator" song before, I think it's a case of folks trying to make a virtue out of a bad design. A reduced size hole does NOT a regulator make, that's confusing flow restriction with pressure reduction, two very different things. If you don't believe it, get a garden hose pressure gauge and the flow restrictor washer from a soaker hose and check the pressure with and without.
To make power in an airgun, you need pressure AND volume. Springers produce about the same peak pressure as most of our PCP's run on, but with a tiny volume of air, that's why even a magnum .22 springer tops out around 25-30 fpe. I've had .177 PCP's that produce almost as much power, and that's just getting started for the larger calibers. My QB build is a perfect example, I'm maxed for power at 30 fpe because of my regs output pressure of 1200 psi, despite the fact that the rest of the design should be good for something close to 50 fpe. At least, that's my theory, and based on the info posted by others, I think it's at least close to reality. I'm sure I've glossed over some of the fine points here, but if I missed something important, I hope someone catches and corrects it
Sounds like someone had that poor Disco of yours seriously tweaked out of shape. I had a Disco for a short time, but I hate the triggers, so it went back to it's previous owner. But like the QB, it's a great platform for modding, and if you have the time, tools, and money, the sky's the limit. But short of a full on custom, there are limits to what the platform is capable of, and you have to respect those limits, or you'll end up with a rifle that's not much use, at best, and potentially downright dangerous at worst. And with that, I need another cup of coffee