Crunch, not all G&Gs use the reverse spring. Many of the ones in Canada (transparent receiver) have normal working releases.
phantastik, you should be able to release the dust cover by a backup means. Find a needle (or anything equally sharp and pointy). Look at the dark block structure on the outside of the dust cover. That houses the catch. Along the top edge of the block, there should be a small hole (it's more elongated than round). Poke the needle into it and push down, that should release the catch and drop the dust cover open.
"The Bird of Hermes is My Name, Eating My Wings to Make Me Tame."