Thread: Projectile vs barrel length

But thats not how internal ballistics perform and the "engine driving the car to the end of the track" is the myth. With even the slowest powder the effect the burn has on the projectile is dropping rapidly after just a few inches of projectile travel down the barrel. The push the projectile has received has it accelerating to the end of the barrel but the rate of acceleration is decreasing.
The best velocity will come from the flattest pressure curve which will be from the slowest burning powder that is suitable for the particular bullet weight, irrespective of barrel length. Any powder still burning after the first few inches of projectile travel will not be enough to effect the rapidly dropping chamber pressure and have no real influence on muzzle velocity. Think of it as if the chamber was a balloon, the powder ignites and inflates the balloon which sends the projectile accelerating down the barrel. A fast powder will inflate the the balloon to its maximum( say 60.000 psi) but the burn is done and dusted so the balloon deflates rapidly. A slower powder will inflate the balloon to max but keep burning and hold the balloon at max pressure for a little longer and exposing the projectile to max presure for longer giving better acceleration
The key here is all of this takes place in the first part of the projectiles journey down the barrel so by the time its traveled a few inches its rates of acceleration are fixed.

Originally Posted by sneeze

But thats not how internal ballistics perform and the "engine driving the car to the end of the track" is the myth. With even the slowest powder the effect the burn has on the projectile is dropping rapidly after just a few inches of projectile travel down the barrel. The push the projectile has received has it accelerating to the end of the barrel but the rate of acceleration is decreasing.
The best velocity will come from the flattest pressure curve which will be from the slowest burning powder that is suitable for the particular bullet weight, irrespective of barrel length. Any powder still burning after the first few inches of projectile travel will not be enough to effect the rapidly dropping chamber pressure and have no real influence on muzzle velocity. Think of it as if the chamber was a balloon, the powder ignites and inflates the balloon which sends the projectile accelerating down the barrel. A fast powder will inflate the the balloon to its maximum( say 60.000 psi) but the burn is done and dusted so the balloon deflates rapidly. A slower powder will inflate the balloon to max but keep burning and hold the balloon at max pressure for a little longer and exposing the projectile to max presure for longer giving better acceleration
The key here is all of this takes place in the first part of the projectiles journey down the barrel so by the time its traveled a few inches its rates of acceleration are fixed.

Agree with you 95%, what you can help me to understand now is, in the case of those people shooting thruout short barrels why or when a slower powder "help" keep the pressure curve till the end of the barrel if the total length is not optimised to the for it?
I do acknowledge all the things "we" are talking here and "I" personally don't have a QL software to check all the possible data and variations the combinations will give "us". I am learning more and more here.

Cheers

Mac

Originally Posted by PERRISCICABA

Agree with you 95%, what you can help me to understand now is, in the case of those people shooting thruout short barrels why or when a slower powder "help" keep the pressure curve till the end of the barrel if the total length is not optimised to the for it?
I do acknowledge all the things "we" are talking here and "I" personally don't have a QL software to check all the possible data and variations the combinations will give "us". I am learning more and more here.

Cheers

Mac

A slower powder will generally give a flatter curve and therefor more area under curve( it will provide peak pressure for a longer time) proving more initial push for want of a better term, better acceleration. How far away the muzzle is has no affect on how fast or hard the bullet can accelerate. You do have to be able to fit enough in the case though which is why we cant just use US 869 for everything, it has to match the chamber and projectile.