Yes
Yes.
Automatic-rifle bullet are usually gas powered and the achieve great speeds by rapidly accelerating out of the rifle, usually in response to a trigger.
No
When a bullet is fired from a rifle or pistol, it has markings impressed on it from being pushed through the rifling in the barrel. These marks, known as striations, are unique to each gun, much as fingerprints are unique. The striations made by two different rifles will NOT be the same. Similar, but under a microscope, different.
You will have to state whether it is a rifle or handgun to get an answer.
He was shot down by a bullet in his heart, apparently fired by a rifle on the ground.
The formula is, quite simply, that the momentum before and after the shot is the same. You can assume that the momentum before the shot is zero (because the rifle and the bullet were not moving), so after the shot, the total momentum will also be zero.
Components include a cartridge case, a primer, powder and projectile- a bullet or shot.
No. A rifle does not have a choke. A rifle has grooves to make a bullet spin around. The spin keeps the bullet going on a straight path. Shotguns have chokes. A choke sits at the open end of the barrell and squeezes the shot just before it leaves the barrell. That squeezing makes the shot hold together and slowly spread out as it goes toward the target. Without the choke, the shot spreads out in all directions as soon as it leaves the tip of the barrell.
As long as the barrel is precisely level with the ground, gravity will pull them to the Earth at the same rate.
Velocity loss is probably in the area of 200 to 300 fps less than a rifle.
Before the shot, total momentum of the rifle/bullet system is zero. Momentum is conserved, so must total zero after the shot. Magnitude of momentum = m V (mass, speed); we'll take care of direction independently. Momentum of the rifle: m V = (3.8) x (2.4) = 9.12 kg-m/sec backwards. We need momentum of the bullet = 9.12 kg-m/sec forward m V = 9.12 ===> V = ( 9.12 / m ) = ( 9.12 / 0.013 ) = 701.54 m/s forward