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Started By
Message
Bapple.........question on barrel length and squib loads
Posted on 4/17/14 at 10:23 pm
Posted on 4/17/14 at 10:23 pm
When looking at "ballistics by the inch," I always come up with a worthless, but still intriguing question:
How long is too long for a bullet to exit a barrel?
I would say that excessive length is not really a 'squib' load, since that is usually due to improper powder loading.
The reason I am asking, if you look at ballistics by the inch, you will see a bullet gathers more fps as the bbl length increases.
But there has to be a tipping point where the barrel's friction will then start to slow the bullet down.......right?
Take 9mm for example.....2 inches is 1130 fps, while 18 inches garners 1460 fps.
Thus stating that it allows the powder to fully burn and push the projectile out faster, the longer it has to travel in barrel.
But where is the equation that then states that the powder is done burning, and then the bullet will then slow in a 28 inch barrel? It has to right? If not, then at what length barrel will the bullet then begin to constantly squib?
Truly worthless question....I, or anyone, has no use for a 30 inch 9mm, but im just curious.
How long is too long for a bullet to exit a barrel?
I would say that excessive length is not really a 'squib' load, since that is usually due to improper powder loading.
The reason I am asking, if you look at ballistics by the inch, you will see a bullet gathers more fps as the bbl length increases.
But there has to be a tipping point where the barrel's friction will then start to slow the bullet down.......right?
Take 9mm for example.....2 inches is 1130 fps, while 18 inches garners 1460 fps.
Thus stating that it allows the powder to fully burn and push the projectile out faster, the longer it has to travel in barrel.
But where is the equation that then states that the powder is done burning, and then the bullet will then slow in a 28 inch barrel? It has to right? If not, then at what length barrel will the bullet then begin to constantly squib?
Truly worthless question....I, or anyone, has no use for a 30 inch 9mm, but im just curious.
2
Posted on 4/18/14 at 12:16 am to dstone12
I won't be able to answer your question but hopefully add a little insight
Not only do you have different barrel lengths but also different bullet weights and different types of gun powder. If you look around at some of the smaller bullet manufacuturers you will find bullets that are claimed to be ideal for shorter barrels. That's because of the faster burning powders used and often times lighter bullets. Different concoctions can and will perform better for longer barrels like you've talked about and on flip side shorter barrels as well.
Not only do you have different barrel lengths but also different bullet weights and different types of gun powder. If you look around at some of the smaller bullet manufacuturers you will find bullets that are claimed to be ideal for shorter barrels. That's because of the faster burning powders used and often times lighter bullets. Different concoctions can and will perform better for longer barrels like you've talked about and on flip side shorter barrels as well.
Posted on 4/18/14 at 2:32 am to dstone12
quote:
dstone12
Your question is very simple and can be almost fully answered with two words:
Burn
Rate
If you have an extremely fast-burning powder (like Bullseye or WST), the bullet will reach it's max velocity much quicker.
If you're using a slower burning powder (like Blue Dot or Power Pistol), the bullet will gradually increase speed and usually peak at much higher velocity than a slower burning powder.
So to sum it up, it all depends on your burn rate. A general rule of thumb when learning about burn rates is that the flashier ones burn slower since you see more powder burn as it leaves the barrel. A faster burning powder will generally be more smoky, and the powders that have an orange flame with sparks is generally somewhere in the middle.
If you see any sort of a flash, a longer barrel would have the potential to allow the powder to burn fully and increase velocity. But if the powder is very fast-burning, a longer barrel could make it eventually get to the point of friction overpowering the burning powder.
Hope this was helpful.
EDIT: +1 on Chessie's comments too. Bullet weight certainly plays a factor as well.
This post was edited on 4/18/14 at 2:46 am
Posted on 4/18/14 at 6:02 am to bapple
Thanks.
I am talking about a control study with say 9mm 115 gr +p for all bbl lengths.
Same powder and burn rate.
The variable is the barrel. Say lengths of 2 in to 35 in.
Somewhere along the study There will be a long barrel that, with the same bullets will begin to trap the projectile due to the length causing so much friction.
At what length would that begin to happen. With the same bullets?
I am talking about a control study with say 9mm 115 gr +p for all bbl lengths.
Same powder and burn rate.
The variable is the barrel. Say lengths of 2 in to 35 in.
Somewhere along the study There will be a long barrel that, with the same bullets will begin to trap the projectile due to the length causing so much friction.
At what length would that begin to happen. With the same bullets?
Posted on 4/18/14 at 10:02 am to dstone12
It would depend on the burn rate specifically, even if they're all the same.
But to put a basic number on it (without any research beforehand), I'd guess probably 100 inches or more. Remember, the bullet is also flying extremely fast and inertia is coming into play.
But to put a basic number on it (without any research beforehand), I'd guess probably 100 inches or more. Remember, the bullet is also flying extremely fast and inertia is coming into play.
Posted on 4/18/14 at 10:06 am to bapple
Y'all need some physicists and engineers to weigh in on this
Posted on 4/18/14 at 11:04 am to Boats n Hose
I think the propelling/expanding gas escaping around the bullet would be a bigger issue than kinetic friction. Once the bullet found itself with equal pressure in front and behind it, acceleration would cease.
Posted on 4/18/14 at 1:18 pm to bapple
Thanks y'all,
Again I think I ask a non practical and silly question.
I just remember back the first batman movie when I was a kid. Joker pulls out that three foot long revolver. Now when I think back to that, I say, "that bullet wouldn't have enough powder to push it out the other end."
It's a non practical question because there is no need for a three foot pistol, you'd go to a .223 rifle, so I understand that.
It's just a physics question about the bell curve or "room temperature" theory where an eighteen inch barrel for a 9mm projectile is optimal for fps, but at some point, additional barrel length will then begin to deteriorate speed.
Again I think I ask a non practical and silly question.
I just remember back the first batman movie when I was a kid. Joker pulls out that three foot long revolver. Now when I think back to that, I say, "that bullet wouldn't have enough powder to push it out the other end."
It's a non practical question because there is no need for a three foot pistol, you'd go to a .223 rifle, so I understand that.
It's just a physics question about the bell curve or "room temperature" theory where an eighteen inch barrel for a 9mm projectile is optimal for fps, but at some point, additional barrel length will then begin to deteriorate speed.
This post was edited on 4/18/14 at 1:47 pm
Posted on 4/18/14 at 3:04 pm to dstone12
this is already done, if you look at burn rate and how it relates to fps you will see your answer in a 44mag/357mag pistol to rifle comparisons
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