If there’s been a study on the flame temperature of smokeless powder, is there a chart showing the differences?
In particular, in shooting say “lever action silhouette” or some other “game” where there are multiple rounds shot, burning temperature may affect the POI of the last few rounds.
When I test ammo, I’ll often let the barrel cool. But in the field or at a competitive game I will shoot as fast as needed.

Finally, double base powders, do they burn hotter?

Sure see e.g. emphasis added to material at http://www.accurateshooter.com/technical-articles/excel-formula-predicts-useful-barrel-life/

For your purposes I might fuss with Tempilaq or otherwise worry more about barrel temperatures than bomb temperature. I'll leave it to you to Google for more information on nitro cellulose or nitro glycerin powder temperatures. I don't know that such information is collected all in one place but the Gun Gack book and others by the same author - John Barsness - mention such at least in passing.

In general, double-based powders do burn a little hotter than single-based powders, but exactly how much warmer depends on the amount of nitroglycerin. One Australian military report (the most detailed I've found on barrel erosion) points out that the nitrogen in nitroglycerin actually hardens the surface of barrel steel a little, counterbalancing the effect of higher temperatures.

Apparently the big factor in bore erosion isn't the exact temperature of the powder burn, but the amount of powder and the duration of the burn. This is why large powder charges for the bore-size fry barrels quicker, and also probably why shooters using some of the newer ultra-progressive-burning powders report quicker bore erosion.

Superb answer, Roomie, and, as usual, totally spot-on.

kd

Thanks, 'dude!

I guess it will take a little trial and error on determining POI changes depending on different powders.

One of my favorite powders for several low pressure cartridges is 4744. An aquaintence suggested using another powder to lesson the heating effect of the powder. In lever action silhouette, obviously the POI change wouldn't be a significant factor I suspect, since it is with iron sights, off-hand and with rifles capable of 1 MOA at best.

But then there's those darn prairie dogs. Heating of the barrels can and usually is significant. (I'm guilty of burning out a barrel during the "heat of the battle" so to speak.) Some rifles don't change POI much upon heating, while some do.

That spreadsheet Clark shared, includes Moly coating. I wonder if Dyna Bore Coating would have a similar affect as Moly since I've chosen to use Dyna Bore and not to use Moly.

IIRC ball powders are double based. Can ball powder manufacturers use additives to reduce the burn temps? I ask because I've gone through many pounds of W748 that had a lower flame temp mention on the label.

https://wwpowder.com/748-2/

Yep, all spherical powders are double-based. (Sorry, I automatically call them "spherical" instead of "ball," because Winchester trademarked the term "Ball" after developing the process. At least one magazine attempts to avoid any legal problems by using the generic term spherical, instead of Ball.)

Powder manufacturers often are pretty closed-mouth about real details, though once in a while they slip up and say something other than the basics. Haven't heard about that one, but they might use a coating that helps it burn cooler.

In a gas, temperature and pressure are "people scale" manifestations of the same micro scale thing: speed of molecules. More pressure = higher temperature.

Can’t make energy without heat.

Run lighter lower pressure rounds if you're worried about barrel heating. I wouldn't be looking at what powder I used so much as how much powder I was burning per round.

which powders do you mean when you say "ultra-progressive-burning" ?

thanx

The allegation is that a powder can produce the same velocity as another without as much heat.

General comment: Temperature and heat are not the same thing.

T

Yup





Same temperature

Quickload lists burn temperature, but I believe it is the so called bomb test (Closed Cylinder) so may not apply the same in a cartridge. I have also read ball powders are less abrasive than stick and reduce wear from un-burnt powder in the throat. This might just be speculation.

Do higher velocities reduce barrel time and somewhat compensate for heavier charges and erosion?

If you want really cool burning powder use black powder.

Real black powder is cool.

For a challenge go PD shooting with black powder. I don't have a flintlock, but a percussion with FF works.

Pick a bullet of a given diameter and weight and lets say you want to push it 3000 fps. You'll need a given cartridge case size to achieve that velocity, and will burn a given amount of powder to achieve that. Your barrel will only last so long. If you want to push the same bullet 3500 fps, you'll need a larger case burning more powder and your barrel life will be shortened.

What you can use is barrel length to increase the accurate life of a barrel. A .308 with a 26" barrel is going to have a significantly longer barrel life than a 300 win mag cut to whatever length matches the velocity. You have less dwell time in the barrel in the 300 win mag, but a barrel will last way longer with a nominal 45 gr powder charge in the the .308 than a nominal 70 gr charge in the win mag.

A larger powder charge headed down the same sized hole will be more corrosive, all things being otherwise the same.

Think of it like sand.

I there's a limit on how much sand I can force down a opening before the opening wears out. Driving more sand and at a higher velocity down the opening accelerates wear.

So, same diameter (.308) with more powder (300 Win Mag) will always wear the throat faster, no matter what type of powder, even if you "loaded down" the 300 Win Mag to 308 velocities.

Erosive

(sic)[/quote]


What you can use is barrel length to increase the accurate life of a barrel. A .308 with a 26" barrel is going to have a significantly longer barrel life than a 300 win mag cut to whatever length matches the velocity. You have less dwell time in the barrel in the 300 win mag, but a barrel will last way longer with a nominal 45 gr powder charge in the the .308 than a nominal 70 gr charge in the win mag.
[/quote]

Not sure I am following this correctly. Are you saying to use a longer barrel to increase velocity instead of more powder? If this then yes but it sounds like you are saying longer barrels last longer?

I was making an example where you can achieve the same velocity with two different chamberings in the same caliber, and have one barrel shoot out much faster than the other. If you want a specific answer, you need to make a specific question.

How long a barrel will last basically comes down to how much powder you burn with each shot. The velocity you achieve has to factor in barrel length. For a given velocity (within reason) you can achieve longer barrel life by choosing a chambering that burns less powder and using a longer barrel.

There's a saying in racing that is perfectly applicable to this discussion. Speed costs money, how fast to you want to go?

Chemicals cause corrosive wear.

For the average rifle barrel, if you multiply the number of rounds doing down the barrel by the bullet dwell time in the barrel, the life of the barrel is six seconds.

I guess my question wasn't clear. There's a lot of answers to other questions, which I didn't intend on asking.

I have an 1898 Krag manufactured in 1899 (with an after market barrel). The accuracy is phenominal for about three shots. Then the accuracy goes Democrat, so to speak. I've shot this several times and the first shots with a cool barrel very good ~ 1 MOA or there abouts with selected loads. (IMR4350 170 grain 30-30 bullets)

My theory is that when the barrel heats the POI changes dramatically since depending on how fast I shoot, the latter shots can bring the group size to 12 MOA or there abouts.

I'm not worried about corrosion, erosion, etc. I do not plan on using this rifle as a bench rest rifle, but plan on hunting with it. I'm not going to shoot enough rounds through this rifle to wear it out. I suspect that I will eventually shoot only cast bullets in it, which I suspect will not heat the barrel nearly as fast as the jacketed loads. I was thinking about using a cast bullet approximately 200 grains and hollow point with the largest diameter bullet that will not interfere with chambering. Cast bullets, at least for me take quite a bit more trial and error than jacketed and I will do this in the next month or two, hopefully,

I feel that the way the barrel and the stock mate on a Krag isn't the best design for placing shots in the same location as the barrel heats.

I've now glass bedded the action and the fore-end tip. There now is a snug fitting front band. But this still is no Remington 700. I noticed that where the front action screw (front trigger screw) there was a gap bewteen the stock and the bottom of the action, which is now filled with glass.

I've not shot the rifle since glass bedding - too many projects.

Finally since this isn't a perfect gas, but is a chemical reaction I do not believe that pressure and heat created by the reaction to be linear with different powders, but I may be wrong.

My question was regarding to temperatures and powders.

Pretty much standard CONOPS on the 'fire is no matter what question you actually asked, us rifle loonies are likely to answer some tangential question we wish you'd asked, so we can wrestle with the trivia of rifle shooting.

Just a bit of trivia....I was using H4350 or something like that (slept since then!) in a 22-250 Ack Imp and 68gr Hornady OTM and the barrel got hot real fast. On a whim I tried N140. Sheboygin! Could shot a whole string before having to let it cool. BTW, that 68gr Hornady was an awesome bullet, I'd use it on deer in a heartbeat. As it was I just used it on coyotes and PDs.

Temperature in a compressed gas corresponds to pressure. That is simple physics.

The Hodgdons powder manuals list pressure with most of their load data. The loads listed with lower pressure will have lower temperature. What is not listed in the manual is peak pressure duration. The duration of peak temperature is just as conducive (or more so) to barrel heating (and flame erosion) as is peak temperature.

It is only simple physics if you are talking about a perfect gas and you are not talking about complex chemical reactions. In this case, this is not a perfect gas and it is a chemical reaction. There is a solid -powder- and a gas -oxygen. The chemical reaction started by athe primer causes the solid to become a gas. The gases created depend on the chemical make up of the solid. The amount of gas is dependent on the chemical make up of ingredients. In this case the change in ingredients is the powder, while oxygen is fairly constant. There are other variables, but unless I quickly move a couple thousand feet in elevation or a severe weather front comes through in the minute or two between shots, these other variable will not have an effect from shot to shot.

The pressure/temperature/volume laws apply whether the gas is ideal or not. The one that doesn't work with complex propellant gasses is PV=nRT. Propellants carry their own internal oxygen and do not depend on atmospheric oxygen.

The amount of gas produced is not linear with the temperatures produced. The other point that I’m making is there are other things that affect the temperature of combustion such as atmospheric conditions. In Spearfish SD the temperature changed from -30 to +40 degrees in 15 minutes. If firing during this period there would be other conditions that have affected the pressure and temperature of the firing of the cartridge. Normally these things can be considered constant as long as the temperature of things like the ammo is constant. Density of air, temperature of ammo etc.
When the ammo is hotter the the combustion is faster. The pressures increase due to the faster combustion. Yet the amount of gas produced is the same as long as there is complete combustion. The bullet will come out of the barrel faster due to the time the bullet is in the barrel there is higher pressure.

However the temperature and the pressure of two solids becoming gases are not linear. You are sticking with your thermo-dynamics story with how gases behave while ignoring the realities of the chemical properties of the different materials changing from solids to gases.

The amount of gas produced and the time it takes for complete combustion is different for different materials.

I am saying that powder “A” can produce the same velocity as powder “B” yet the temperature produced can be different all other things being equal.

The amount of gas produced is not linear with temp. The amount of gas produced is dependant upon propellant charge.

The pressure of that gas is linear with temperature.

Lots of external factors effect pressure/temp during ignition of a powder charge. The most important factor being barrel steel temperature. Compare the ignition cycle of the same rifle at two extrem temperatures. If a rifle is minus 100 degrees Celcius when it is fired, the barrel will suck many calories from the chemical reaction of the propellant, muzzle velocity will be reduced because heat was robbed from the reaction and lowered chamber pressure.

Compared to the same rifle fired at 200 degrees celcius. The barrel steel is three hundred degrees warmer, and while it is still much cooler than flame temperature of the powder charge, it will absorb much less heat from the reaction than the colder barrèl. Possibly allowing temperature and pressure to elevate far enough to become dangerous.

All of us have seen the variatons in muzzle velocity produced by shooting in varied temperatures. While we obviously do not shoot in the extreme conditions I portrayed, I have test fired rifles from minus 15 F to 110 degrees F. The differences in muzzle velocity are easily recorded and are solely dependant upon changes in chamber pressure.

If powder A produces the same velocity as powder B with powder A having a lower temperature, powder A also delivers a lower pressure. There are many examples of this., because the duration of powder B is longer.

Take for example the 30-06 with a 150 gr bullet. From Hodgdons #26, H322 at 46 gr will produce 2720 fps at 50700 cup. While H414 at 58 gr will produce 3043 fps at 48700 cup. H322 is the hotter of the two powders. It produced the highest temperature and highest chamber pressure. But H414 produces more gas because it uses more powder to start with. It produces more velocity at lower temperature because the pressure, although lower, is sustained over a greater period of time

Give or take some carbon residue and unburned powder, the mass of the gas equals the mass of the powder, just as Idaho Shooter said.

Smokeless powder converts almost entirely to propellant gas.

"Lots of external factors effect pressure/temp during ignition of a powder charge. The most important factor being barrel steel temperature. Compare the ignition cycle of the same rifle at two extrem temperatures. If a rifle is minus 100 degrees Celcius when it is fired, the barrel will suck many calories from the chemical reaction of the propellant, muzzle velocity will be reduced because heat was robbed from the reaction and lowered chamber pressure.

Compared to the same rifle fired at 200 degrees celcius. The barrel steel is three hundred degrees warmer, and while it is still much cooler than flame temperature of the powder charge, it will absorb much less heat from the reaction than the colder barrèl. Possibly allowing temperature and pressure to elevate far enough to become dangerous."

i'm neither physicist, ballistician nor engineer but, in your example of a barrel at -100 degrees or 200 degrees if the cartridge is room temperature when placed in the chamber and fired is there adequate time for barrel temperature to have a profound effect on gas pressure or volume ?

thanx

[quote=denton]

The Mass of the gas is one thing. The volume of gas is a whole different matter.

Of course.

Different topic......

A wrong idea that gets repeated over and over is that it's the initial temperature of the powder that affects muzzle velocity. Actually, it's just as was stated by Idaho Shooter: Cold steel robs more heat energy out of the gas than hot steel does. Ammunition temperature matters a little, but only because the brass and lead rob energy as well. Barrel temperature is about 3X as influential as brass and lead temperature.

Gas will expand to fill all space available, therefor volume (in the way you are using it) of gas is a non-relavant factor. Mass of the gas (more accurately, the number of gas molecules) times temperature devided by volume of containment vessel yields pressure.

This is why pressure and temp are linear.

As to barrel temp vs pressure: Denton has done the experiments and shown us the data. He knows that of which he speaks.

There’s three variables in the thermodynamic formula referred to as simple physics. This formula is valid in certain and certainly in what we’re discussing.
Pressure temperature and volume.

If volume is constant then a rise in temperature will subsequently cause a rise in pressure.
If volume is not held constant say absolute temperature is raised by ten percent and volume of gas in a confined space is also increased by ten percent, what is the resultant pressure?

Similarly if a solid sublimes or due to combustion creates gas, depending on the type of the gas produced, different amounts, in volume, of gas will be produced.

An extreme example. A frozen block 6 grams of hydrogen and a frozen block 6 grams of CO2 are thawed. The the gas produced will be 6 grams. Now if those gases are contained in one cubic meter, and the temperature is zero degrees C. The pressure inside the container of hydrogen will be greater than the container with CO2.

Now, consider the different chemical mixtures of powder.

I think you are making the problem more complicated than it really is. Let me try my hand at simplifying:

For any mixture of gasses, P1*V1/T1 = P2*V2/T2. Temperature has to be in Kelvins. This applies to the mix of CO2, N2, H2, etc. that is produced by propellants as well as it applies to a pure, ideal gas like Argon.

Now if you want to calculate pressure and temperature from volume, number of moles of gas, etc., the problem is as complicated as you think it is. But as long as you stick to the same mixture of gasses, you can fiddle with temperature, pressure, and volume using the formulas above. Fortunately, that's often enough.

That is the point! The same mixture of gasses or could I say the different mixture depending on the chemical make up of the powder. I don’t know if two powders that are the same, unless H110 and Win 296 or something such as that.

You're right. I would not depend on two different powders delivering the same mix of propellant gasses. Single base and double base would almost surely yield different gas mixtures.

Unless there is some great simplifying assumption that I don't know about, working out the pressures and temperatures from basic principles will produce a major headache.

Comparing a mix of gasses at one pressure, temperature and volume with the same mix at a different temperature, pressure, and volume is no problem.

Edited to add: Maybe it's not as horrendous as I thought. You should be able to get a temperature from the emission spectrum of gas as it exits the muzzle. You know the pressure at that point, and should be able to work back to the peak pressure and temperature. Maybe. I guess.

Yes, absolutely. Because there are more moles in 6 grams of H2 than in 6 grams of CO2.

But when we talk about the combustion of powder charges, the resultant gases are remarkably similar, even though the powders may be of dissimilar burn rates. All of our powders are composed nitro glycerin combined in some percentage (possibly zero) with nitro cellulose.

No, the gases produced by burning Bullseye are not identical to the gases produced by burning H870. But they are close enough to give us two or three significant digits of accuracy. With all the other vagaries involved firing a rifle cartridge, distance from the lands, chamber dimensions, lubricity of the bullet, rounds since last cleaning, actual internal volume of each piece of brass, actual temperature of the barrel at the time of the shot, etc, etc, etc. A couple of significant digits is as close as we can come.

The simple point being you can not get to 65,000 psi by burning powder without a spike in temperature, and it takes a higher temperature to make 65,000 psi than it does to make 55,000 psi.

From dim memories: didn't Hodgdon rename the surplus spherical powder WC-846, to BLc lot 2 , the c standing for cooler burning? How did he determine it was actually cooler burning?

I think you got those backwards, nitro cellulose is the primary constituent of smokeless powder, nitro glycerin is added to double base powders. Straight nitro glycerin would tend to go boom instead of bang.

Uh.....yes.....that is what I said. Some percentage, possibly zero, of nitroglycerin.....mixed with nitrocellulose.

Okay, I do see how my meaning could have been misconstrued. While English is my first (and only) language, it might be hard to discern that from my writing. English classes always depressed my GPA from the straight A's received in Math and Science.