Type of rifling/twist.
A round is loaded into a gun. The gun is then cocked and then fired.
No
depends on which 9mm and which gun. The 9mm Parabellum (9mm Luger) fired from an average pistol travels ABOUT 1200 feet per second.
It depends on exactly what you mean. If you fired a round in a gun and the actual projectile is stuck in the barrel, you should take the gun to a gunsmith and have him tap the bullet out using the correct tools. If you are having malfuctions such as a double feed, simply go to a reputable gun shop or gun range and ask someone to show you how to clear the malfunction. Take the gun in to the shop in a gun case of some kind, and tell the person what you need, and be sure to tell them the gun is loaded and a round is stuck. Don't just walk in with a gun in your hand.
science, Bullet markings and check them with the rifling of the firearm. Barrel twist and or markings can help ID the gun fired from. Nothing can tell you for sure, It can just tell you it was fired from a barrel like that of a type or make.
If a round is not fired and then ejected, nothing comes out of the barrel.
A round is one shot, or cartridge. The term 'round', for the projectile fired from a gun, comes from the days of the musket when the ammunition was round. The projectiles are no longer roung but the name stuck.
I'm assuming you're asking if a .380 round can be fired in a 9mm handgun. The answer is, yes, it may be possible, but it is not a good idea to fire any cartridge in a gun other than the correct caliber for that specific gun.
No, but, they are able to use forensics to tell if a weapon fired a projecitle if they have an example.
When a gun fires, the primer and burning gunpowder eject residue. That residue is chemically like very few things OTHER than gunshot residue (GSR) If your clothes test positive for GSR, it is a pretty safe bet you were very close to a gun that was fired. It may or may not tell whether YOU fired the gun.
A bullet fired from a gun
In many cases, chemicals from the gunpowder and from the primer will transfer to the hands and clothing of a shooter. This can be found in a lab test.