What could happen to me for braking the factory test bullet envelop of my hangun ?

Absolutely nothing. That test bullet casing is only there to pacify one states criteria, if you are in possession of that bullet casing you do not live in that state.

They take away your gun and throw you in jail.

(The Toad is correct. I was just teasing.)

If one of mine got lost and John Law needed to clear my gun... he'd test fire one of his in the good old forensic department.

Spent cases have several points to match up... chamber scratches, firing pin indentations , extractor/ejector marks- None are 100% conclusive for match. As a firearm wears from use it may be argued (with some certainty) that the marks will not match that sealed case.

Maybe that's why it was a "feel good" liberal law and Maryland ran out of space to store all those cute little envelopes?

Paper cut.

The spent cartridge is provided so I can be provided to your state government if they have a ballistic fingerprinting database. Most don't. And Maryland recently scrapped theirs. So nothing will happen.

Nothing if you live in a state where it was still in your pistol box

Nothing in a free state.