Bullet speed

[jeffconusa]

Can anyone tell me the answer to this question with scientific proof?
(not seat of the pants reasoning)

If you shoot a bullet from a 20 inch barrel and ALL of the powder is burned by the time the bullet gets to the muzzle, will the bullet speed be the same if you switch to a 26 inch barrel? Every one tells me that the longer barrel will result in a higher velocity but this does not make sense since all the energy from the powder has been generated and used.

 

[mattmc40]

Re: Bullet speed

I was told one time that in a 308 the barrell length for all the energy from the powder completely burning would be around 38 inches? This info came from FBI ballistics guy.... A barrel 20 inches would be a slower than a 26 incher except from some of the crazy loads some guys run!

 

[FCS]

Re: Bullet speed

Gas is still expanding.

 

[letitsnow]

Re: Bullet speed

As long as the force of the gasses on the bullet are greater than the drag of the barrel on the bullet, the bullet will accelerate. Once the powder burns, even after it's all gone, there is still a significant amount of pressure behind the bullet. Only when the drag is greater than(or equal to) the force of the hot gasses, will the bullet decelerate(or move at a constant speed).