Rates-of-twist

[LME]

The burn rat of black powder is anything but instant, that is why the barrels got longer so that more of the powder charge had time to burn. Doesn't matter what kind of powder you use a longer heavier bullet requires a faster twist to stabilize it.
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The burn rat of black powder is anything but instant, that is why the barrels got longer so that more of the powder charge had time to burn. Doesn't matter what kind of powder you use a longer heavier bullet requires a faster twist to stabilize it.

I would like for you to explain to me why magnum rifles have fast twist and require slow burning powder? If you use a fast burning powder like imr 4831 it produces a lot of presure fast and is not condusive to magnum rifles? If you use imr4064 it works extremely well in mid range calibers and it happens to be in the mid range in burning rate. As far as the burning rate of black powder compared to smokeless it is fast burning. Why do you think black powder was used for blasting before the invention of dynamite? Smokeless powder burns to slow to be used very well for blasting. There is a reason magnum rifles have longer barrels than regular calibers. It needs the extra length to use slow burning powder.

 

[ronaldrothb49]

I would like for you to explain to me why magnum rifles have fast twist and require slow burning powder? If you use a fast burning powder like imr 4831 it produces a lot of presure fast and is not condusive to magnum rifles? If you use imr4064 it works extremely well in mid range calibers and it happens to be in the mid range in burning rate. As far as the burning rate of black powder compared to smokeless it is fast burning. Why do you think black powder was used for blasting before the invention of dynamite? Smokeless powder burns to slow to be used very well for blasting. There is a reason magnum rifles have longer barrels than regular calibers. It needs the extra length to use slow burning powder.

You kind of contradict your own argument. If black powder is so fast burning then why did they go to longer barrels? If black powder produces pressure so much faster then why are muzzleloading barrels listed for only black powder only, wouldn't you be able to safely use them for modern powders? If you look at any rate of burn chart for powders black powder is going to be on the bottom. Actually dynamite was invented in 1867 quite a while before smokeless powder existed.

 

[Artificer]

LME said:
One thing that I haven't seen is the rate of burn of black powder. Black powder is almost instant and modern smokeless powder varies. The fact that smokeless powder can be fast burning or slow gives the shooter many options that don't fit well with Black powder users. Some people think the faster a powder burns the faster the bullet. The facts are totally different. Slow burning powder produces more gas therefore more speed behind the projectile.This makes a fast twist just about the only thing we black powder shooters have to get a heavy long projectile stabilised.

The burn rat of black powder is anything but instant, that is why the barrels got longer so that more of the powder charge had time to burn.

With respect, the London Royal Society proved this was not true around 1750, though it continues to be one of the biggest false myths about black powder to this day. Back then, they used the exact same pistol powder charge in a pistol with the same size ball, but started out with a long barrel and then progressively cut back the barrel. They stopped when they got to the barrel being only 1 inch longer than the combined length of the powder and ball and ALL the powder that was going to burn inside the barrel, burnt up in that short of a barrel. Because you have a larger charge of powder in rifles, smoothbore long guns and muskets, it takes a little longer for the powder to burn, but still ALL the powder that is going to burn, burns up within a few inches from the breech at most.

The real reason bullets come out faster out of longer length barrels with the same powder charge, is basic physics. Longer barrels give the Gas Pressure from the burnt powder, more time to push on and increase the speed of the projectile inside the barrel. Though this is not an exactly similar comparison, most people who have ever pushed a car to get it started know that it takes the most force to get the vehicle initially rolling. After that it doesn't require as much force to keep it rolling. Matter of fact if you continue to push with less force than was needed to get it moving, the vehicle will speed up as it goes along, until you pop the clutch to start the car.

Gus

 

[Artificer]

You kind of contradict your own argument. If black powder is so fast burning then why did they go to longer barrels?

Already answered that in the post above.

If black powder produces pressure so much faster then why are muzzleloading barrels listed for only black powder only, wouldn't you be able to safely use them for modern powders?

Black Powder produces pressure faster BUT does not produce anywhere near the amount of pressure of most smokeless powders. This is how they got away with using dead soft iron barrels or bronze for so many centuries with Black Powder. Though modern barrels for BP are made of steel, they are made from a steel alloy that is strong enough for black powder, but not strong enough for the higher pressures of smokeless powder. If they used the same steel alloy that black powder barrels are made from in your .30-06, it would cause the barrel to open up like a banana or pieces blown out from the breech.

Gus

 

[Old Hawkeye]

I would like for you to explain to me why magnum rifles have fast twist and require slow burning powder? If you use a fast burning powder like imr 4831 it produces a lot of presure fast and is not condusive to magnum rifles? If you use imr4064 it works extremely well in mid range calibers and it happens to be in the mid range in burning rate. As far as the burning rate of black powder compared to smokeless it is fast burning. Why do you think black powder was used for blasting before the invention of dynamite? Smokeless powder burns to slow to be used very well for blasting. There is a reason magnum rifles have longer barrels than regular calibers. It needs the extra length to use slow burning powder.

Twist rates are no different for a "Magnum" round than a non-Magnum round of the same caliber & Magnum rounds do not necessarily "require" slow burning powder. You have been given some incorrect information. Slower burning powders generally give higher velocities with heavier for caliber bullets. IMR 4831 being consider as having a "fast" burn rate is a new one on me, but I guess everything is relative. Powders considered slow in one caliber can be considered fast in a different caliber. Trying to somehow equate burn rate of powders & twist rate of rifling makes no sense & I have no idea want your point is, as the burn rate of a powder has nothing to do bullet stability.

 

[LME]

Twist rates are no different for a "Magnum" round than a non-Magnum round of the same caliber & Magnum rounds do not necessarily "require" slow burning powder. You have been given some incorrect information. Slower burning powders generally give higher velocities with heavier for caliber bullets. IMR 4831 being consider as having a "fast" burn rate is a new one on me, but I guess everything is relative. Powders considered slow in one caliber can be considered fast in a different caliber. Trying to somehow equate burn rate of powders & twist rate of rifling makes no sense & I have no idea want your point is, as the burn rate of a powder has nothing to do bullet stability.

You believe what you want to. I had to study to learn the little bit I know. You should read a few books on the subject.

 

[Old Hawkeye]

You believe what you want to. I had to study to learn the little bit I know. You should read a few books on the subject.

Can you provide any data, documentation, or evidence that powder burn rate has any influence on bullet stability? I ask again, what's your point??? What is your argument??? Why are you rambling on about powder burn rates when the thread is about twist rate & bullet stability??? You may want to study some more & read some more books! Just sayin'.

 

[waksupi]

A center fire rifle requires faster twist on heavier bullets to establish stability.

 

[doubleset]

The formula to determine the Rotational Velocity in revs/sec is ... Wrong formula! ...

It is nice to see these sorts of details actually worked out with some precision. One of the most useful calculational tools I learned when a junior in high school (though at an NSF summer program) was dimensional analysis. It should always be applied to your calculations in physics as a relatively simple and quick check that you haven't made a simple blunder in converting dimensions -- which is very easy to do. (In fact, it was also offered as a method by which one could arrive at the correct equation for performing a particular calculation.) Later, this simple approach to checking a fundamental feature of your engineering calculations saved me an untold number of errors on physics and chemistry tests. I still use it today, but with somewhat less frequency.

 

[doubleset]

Can you provide any data, documentation, or evidence that powder burn rate has any influence on bullet stability?

We don't need no steeking evidence! We ride by our feelings and intuitions, eh? What kind of man are you?

 

[recurvebill]

Well , read both pages on this thread , and come to the conclusion that (1) this is the best darn site of this type out here , (2) during my reading i was distressed , repressed , and impressed by what i read , & , (3) guess i will just keep makin' smoke with what works for me . BTW , had a 1in32 barrel gun once , and it was a much better shooter with conicals than i was . Did not like the looks of it , so, traded for a "surf rod and reel" , and think i got the better end of that trade !! Keep makin' smoke fella's , it is all good !!!

 

[Mr. Flintlock]

One thing that I haven't seen is the rate of burn of black powder. Black powder is almost instant and modern smokeless powder varies. The fact that smokeless powder can be fast burning or slow gives the shooter many options that don't fit well with Black powder users. Some people think the faster a powder burns the faster the bullet. The facts are totally different. Slow burning powder produces more gas therefore more speed behind the projectile.This makes a fast twist just about the only thing we black powder shooters have to get a heavy long projectile stabilised.

Black powder is an explosive. Gun powders are fast burning propellants.

 

[Old Hawkeye]

A center fire rifle requires faster twist on heavier bullets to establish stability.

What are you trying to say? What point are you trying to convey? Some centerfire rifles can have a 1:38 twist & others can have a 1:7 twist. It's not the rifle that requires a "faster twist", but rather the bullet being used. It's not the "weight" of the bullet that dictates the required twist rate for a bullet, it's the LENGTH! Just so happens that most, but not all, of the time the heavier a bullet the LONGER it will be, which is how the "heavier" bullets require a faster twist belief got started. I have Hornady 140 grain plastic tipped 6.5mm bullets that are nearly 1/4" longer than my Lapua 155 grain round nose 6.5mm bullets. The 155's will stabilize in a 9.5 twist while the 140's will not. Kind of blows the common misconception about "heavier" bullets "require" a faster twist out of the water.

 

[Mr. Flintlock]

Long bearing surface bullets require fast rifling to stabilize the bullet in flight. 500 plus grain bullets sometimes won't stabilizing until they're out 200 - 300 yards.

 

[Mr. Flintlock]

Think of a spinning top, when it first starts to spin it wobbles a little bit then it stabilizes. The faster it's spun, the faster it stabilizes.

 

[Siringo]

From GOEX msds publication:


VELOCITY
In the open, trains of black powder burn very slowly, measurable in seconds per foot.
as in steel pipe, speeds of explosions have been timed at values from 560 feet per second for very coarse granulations to 2,070 feet per second for the finer granulations. Confinement and granulation will affect the values

 

[Mr. Flintlock]

If you try to push a bullet out of a barrel too fast, the bullet can skip the lands and not spin. No spin, no accuracy.

 

[doubleset]

Black powder is an explosive. Gun powders are fast burning propellants.

This gets repeated with surprising frequency. It is at least misleading if not outright false, and the point of saying it is unclear.

First, black powder is (certainly used as) gun powder. So it doesn't make much sense to say that black powder is an explosive but "gun powder" isn't. To talk about "black powder" vs. "gun powder" is to confuse a chemical/physical description (in terms of composition and properties) with a functional one (what the stuff is used for). A lot of people seem to believe that the distinction is that black powder "detonates" but smokeless powder does not, but smokeless powder will in fact detonate quite easily, and this is why it can be used to make bombs.

Next, so-called "smokeless powders" are in fact universally regarded in law and regulation as a "type" of explosive, and certainly can be employed to cause explosions in any reasonable sense of that term. Black powder is classified in the federal Code of Regulations as a Class 1.1 explosive, and smokeless powder is classified as a Class 1.3 explosive. "Explosive" is defined in that context as "... explosive means any substance or article, including a device, which is designed to function by explosion (i.e., an extremely rapid release of gas and heat) ...". But note that the distinctions imposed in these classifications here in the Code are within the context of an unconstrained "burning" of the substance itself and don't consider the phenomenon of explosion when the substance is constrained (as, for example, in a cartridge, some sort of a container, a gun barrel, or a pipe bomb).

There is a technical distinction between detonation and deflagration, and between primary and secondary explosives (not to confuse that with a distinction between low and high explosives). It's all a bit complicated and technical in terms of the actions that take place at the molecular level and how that affects rate of combustion, etc., but yeah ... what we call "smokeless gun powder" is an explosive, and there's no useful point in saying it's not.

A good amount of the detail of this, presented in an understandable way and without lots of math is here:

Characteristics and Manufacture of Spherical Smokeless Powders​

You can make distinctions and split hairs about what "explosive" means and how the word should be used, and in certain contexts there may be some point to that. But in any normal sense of the term (including in both physics and law), both black powder and smokeless powder are explosives -- and any distinction you want to draw at least needs to make clear what your purpose is on insisting on calling the one "explosive" and the other not. The whole subject of explosive/non-explosive is also discussed in any number of other places on the web. You just have to look.

 

[LME]

Can you provide any data, documentation, or evidence that powder burn rate has any influence on bullet stability? I ask again, what's your point??? What is your argument??? Why are you rambling on about powder burn rates when the thread is about twist rate & bullet stability??? You may want to study some more & read some more books! Just sayin'.

I may not have been clear enough in my statement. Simply put, long heavy bullets in M.L. prefer a fast twist and when B.P. is compared to smokeless it is fast burning. it isn't to say that a slow twist will not shoot a long heavy bullet , we all know it will but not with the accuracy one would want. The bullet will not be stable. If the power burn is slowed down a bit it produces more gas to propel the bullet this means you could have an even faster twist and a stable bullet like some modern arms that have a 1 in 10 twist and propel a little short bullet. A fast twist in a M.L. is a slow twist in a modern rifle. When slowing down it is milli-seconds or even slower which doesn't sound like the word slow fits but it does.I hope this clears this up?

 

[doubleset]

... when B.P. is compared to smokeless it is fast burning.

I'm not sure what you intend the scope of this claim to be. In "free air" (i.e., unconstrained in something like a cartridge or a barrel), smokeless powder burns relatively slowly compared to black powder. But who cares about that unless you just like to watch stuff burn in open air? What would clear some of these things up is reference to a well-documented and supported burn rate table which describe the precise conditions under which measurements were made. Otherwise, it's just "he said/he said". We do know that when confined, smokeless powder exhibits a much steeper pressure curve and rate of burn than when burning freely in air, and a much steeper pressure curve than does black powder (at least most smokeless powders do). Basically, when B.P. is compared to smokeless in a gun barrel, it is much faster burning -- at least at and beyond a certain point in its combustion, and this is precisely why it can produce such higher muzzle velocities.

Also, I'm quite confused by the claim that "If the power [sic] burn is slowed down a bit it produces more gas ...". I guess by this you mean that if the burn rate is decreased, then more complete combustion (=> more gas) will result.. But this would be so only if there is sufficient time for the lower combustion rate to result in sufficiently more complete combustion before the bullet is out of the barrel. For a given barrel length, it's far from obvious that lowering the powder burn rate would in fact result in more gas, and so result in a higher muzzle velocity for the bullet. Is this just a thought experiment that you're putting out? Or can you point to any data supporting it -- and precisely what the variables are that might affect the results? Or have I just missed the point?