Pulmonary artery is pretty hard core but like anything else it depends on how bad the damage is. If its just a little nick then a little quick clot and you'll be fine. Completely sever it and you can still survive it but only if you have someone to help stem the blood loss and get you immediately to the hospital. Even with quick clot and constant pressure, you're talking maybe 30 minutes.
A bullet permanently lodged in the lung? Well, the limit of my expertise on this subject is the immediate care of a wound. I really don't know anything about the long term effects. I don't remember where I heard this but I vaguely remember hearing that any solid object in the lungs will cause the lung to... do something or other that would hurt your ability to breath. Was it grow scar tissue? Fill with fluid? It was one of those things I overheard but didn't pay attention to because I didn't care at the time, so maybe someone else can elaborate. The breaking burgundy said, the brain can take a lot. Go read the case of Phinneus Gage. This guy got a railroad spike through the brain, which caused brain to squeeze out of his head when he sneezed, and survived for quite a while afterwards.
