Bullet acceleration after leaving the barrel?

Question

How many people do not realize that the friction of the bullet sliding against the barrel is greater than that of the "air pressure" outside the barrel and that the "air pressure" inside the barrel IS the same or MAY be greater than that of the "air pressure" outside of the barrel when constrained by the walls of the barrel and by the force of a rapidly moving bullet?

That's exactly my point. That once free of the friction from the barrel the bullet enters the significantly less friction atmosphere of the outside air. Also, for those that know a little about aerodynamics, since thrust opposes drag, and there is little drag or negative pressure behind the bullet because the gas is also rushing out of the barrel and is still expanding in a forward direction with some loss to the sides of course the bullet will continue to accelerate in feet per second from the end of the muzzle.

Someone brought up a good point, some cartridges do meet their maximum pressure inside the barrel. Others do not and the gas pressure is still pushing and expanding just as a bomb does after it leaves its casing. In fact it is the unrestrained pressure wave that gives a bomb it's concussive force.

Have any of you who seem to already know this answer ever gotten out to the range with two chronographs and tested it?

"the friction of the barrel is lost while the force driving the bullet remains"

That would be incorrect. The force driving the bullet overcomes the friction of the barrel. Once the barrels friction is lost, i.e. the bullet leaves the barrel, the acting force has less resistance to overcome therefor more of the energy is used to accelerate the bullet and none is used to overcome the friction. plus the bullet has little drag due to the air rushing out behind it.

Answer 1

The air pressure distribution round a bullet is very complex, but if the net force from air pressure is zero, there will be no acceleration due to air pressure.

There will be air friction slowing the bullet down, and gravity, accelerating it downwards.

The exact acceleration will depend on how these things combine.

It is possible for a bullet to accelerate once it has left the barrel of a firearm however, the distance in which this happens is so small that it can not be considered for ballistics. We are talking about 10 thousandths' of an inch in general terms. Newton's Law is a general law and does not take into effect the second that the bullet leaves the barrel, the friction of the barrel is lost while the force driving the bullet remains !

Good Luck & Happy Shooting !!!

**Edit**

I have never tried it but, I will be going to the range this weekend and I will. Im just not sure if i can set the graph close enough together to see the increase after the barrel. I will let my wife do the shooting and see if i can get some hard numbers while she does. I know its been done and proven, Im just not sure if I have enough equipment to get an exact numbers. I will email you if I can !

Answer 2

At the point the bullet clears the muzzle the pressure acting on the base is rapidly reduced, acceleration can not happen. Yes gas is faster than the bullet and will envelop the bullet on its exit this reduces the air resistance that was set up BEFORE the bullet escaped the muzzle. Please physically prove that there is acceleration and then tell us what that distance is if it is so .

Answer 3

and that of the gasses being pushed through the barrel, making the bullet spin in the barrel but as it leaves it starts to tumble because of the turbulence it produces. when it leaves the barrel is also called the muzzle velocity

Answer 4

oh but the pressure of the expanding gases from the gun powder is grater in the cofained space of the barrell

Answer 5

What's your point? Bullets do not accelerate once they've passed the muzzle of the barrel.

Answer 6

Well, I'm pretty sure without the rifling inside your barrel, all that speed wouldn't do you much any good.