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Discussion Starter · #1 ·
does fast burning powder develop more psi than slow burning powder in same caliber and bullet weight?
 

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Discussion Starter · #3 ·
Thank you Ridgerunner665.
is there a way to calculate psi or is it measured?
 

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I'll second the "Don't Attempt To Guess".

There is no practical way for a non-commercial reloader to gauge PSI, CUP, or any other pressure measurement.

Luckily most of the big component manufacturers do it for us. Get two or three manuals, crosscheck and follow the loading formulas and you should be good to go.

Even standard 'pressure signs' during firing and on spent casings can lie or be misinterpreted. Stick to the books and established baselines. If you can buy or borrow a chronograph, it's a useful tool for keeping you in safer realms. Maxing out the pressure isn't the pinnacle of reloading. Many posters here will merrily tell you that the best shooting load for their gun is quite a bit under max.
 

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Discussion Starter · #6 ·
thank you for your replies and advice.
I use Hodgodon load data and their powders.
Just wanted some answers, knowledge is good, it allows you to question
what is written.
 

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Hunter,
BEFORE you start reloading you had better do alot more reading !!!!!!!!!!

Remember the saying----A LITTLE BIT OF KNOWLEDGE IS DANGEROUS !

Hip
 

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Pegasus said:
Are you saying that fast powders have more chemical energy grain for grain as compared to slow powders?
I'm saying faster powders release it (the energy) faster...the faster a powder burns, the more the pressure builds before the bullet has time to move.
 

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I'll agree that fast powders hit their energy curve sooner. However, I wouldn't want to definatively say that faster powders = a GREATER pressure curve.
 

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Thren68 said:
I'll agree that fast powders hit their energy curve sooner. However, I wouldn't want to definatively say that faster powders = a GREATER pressure curve.
With the same charge weight...the faster powder will always have a higher peak pressure.

Don't confuse the "amount of pressure" with the "pressure curve"...2 different things.

If you're basing that opinion on muzzle velocity you're looking at it from the wrong end. A longer pressure curve will almost always yield higher velocity, this is the advantage of slower powders.

An example (45acp)...say, 8 grains of Power Pistol under a 230 grain TMJ, that load is appx. 19,000 psi. (longer pressure curve)

Now, 8 grains of Bullseye :eek: is a whole nuther monster...and will disassemble most pistols. (high pressure spike...not much "curve" to it)


OR, if you take it to extremes (this is the "almost" I mentioned above)

45-70, 50 grains of Varget under a 405 grain bullet...a powder puff load. (18,600 cup)

50 grains of H4198 under a 405 grain bullet....(39,000 cup)

Faster equals higher...
 

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Since the poster was asking about same caliber and bullet weight, then I think the answer would be no, as long as load data was followed. The difference between fast and slow powder would be as to when the pressure peaked on firing. I don't think he was asking about the same charge weight between the two powders.

Fast powders are desirable in a handgun because there isn't much barrel length to contain the pressure needed to reach desired velocity before the bullet exits. Use fast powder in a rifle and you lose pressure and velocity as the bullet travels down the barrel because pressure peaked to soon, thus the use of slow powder to maintain pressure the full length of the barrel.

Pressure curve and peak pressure are very much related. Velocity is the result of pressure. Fast powders reach the desired velocity sooner than slow powders but it still takes the same pressure from each to reach that velocity and that pressure needs to be maintained the length of the barrel. Least ways that's the way I understand things.

Of course 8 grains of Bullseye could be harmful to the gun and shooter in a 45 ACP because it is a over load. One can accomplish the same thing with just about any powder whether fast or slow burning.
 

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Gohon said:
Of course 8 grains of Bullseye could be harmful to the gun and shooter in a 45 ACP because it is a over load. One can accomplish the same thing with just about any powder whether fast or slow burning.
Everybody is missing my point or I'm not making clearly...not sure which.

The 8 grains comparison was a comparison of pressure per grain of powder...no slower powder is going to produce that pressure with an 8 grain charge.
 

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The 8 grains comparison was a comparison of pressure per grain of powder...no slower powder is going to produce that pressure with an 8 grain charge.
I understood what you were saying and I think most did. You are correct that grain for grain a fast powder should read higher in psi. My point was the OP was asking about using the same caliber and bullet weight and if faster powder would be at a higher psi than slower powder. My answer was it would not, as long as load guidelines were used to reach the same velocity from each powder. Naturally it should take less fast powder (fewer grains) than slow powder in a short barrel firearm to reach the same velocity but pressure should be about the same from each load if held within guidelines for the same caliber and bullet weight. I didn't think he was asking about a grain for grain comparison but maybe I misunderstood his question.
 

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Discussion Starter · #15 ·
sorry for the confusion in my question.
I did mean grain for grain.
 

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Just so we are clear, faster powder has the same amount of chemical energy as slower powder. It's just that a faster powder will release that energy more quickly than a slower powder and so for the same space it will attain a higher peak pressure until the bullet starts moving (the initial kick.) The slower powder will keep pushing the bullet after it has started moving.
 

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In that case Ridgerunner is absolutely correct in his answer to your question...........

Pegasus, is that a higher peak pressure or a faster peak pressure? I thought slow powders would reach pretty much the same peak pressure but just farther down the curve. I also thought that was the reason for going to a slow powder when shooting pistol cartridges in a rifle instead of the normally recommended pistol powders.
 

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"There is no practical way for a non-commercial reloader to gauge PSI, CUP, or any other pressure measurement."

Not only can WE not 'gauge' a burn rate:pressure measurements, neither can the 'pros.' They have to do some quite elaborate lab testing to determine the burn rates of every powder production lot. Fortunately, we don't need to be concerned about it; we pay the loading manual makers to provide us all the info we need or can intelligently use about such things.
 

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Gohon said:
In that case Ridgerunner is absolutely correct in his answer to your question...........

Pegasus, is that a higher peak pressure or a faster peak pressure? I thought slow powders would reach pretty much the same peak pressure but just farther down the curve. I also thought that was the reason for going to a slow powder when shooting pistol cartridges in a rifle instead of the normally recommended pistol powders.
Ridgerunner couched his statements very well.

It is my understanding there are two types of gunpowder; single base and double base. Single-base is all nitrocellulose and double base has some nitroglycerin added for a little extra vigor. Smokeless gunpowder is a propellant and its job is to burn quickly and generate lots of hot gases. For a given volume of powder, you will get about 1000 times that volume in gas, at the same temperature and pressure, of course. Since the powder is placed in a small container it will generate its 1000-fold amount of gas but this gas will be under heavy pressure because of the confinement of the vessel. Gunpowder burns quickly and fairly completely under pressure, as opposed to when it burns in the open.

Gunpowder is manufactured in granules that have different forms: ball, stick, flake, cylinder, etc. These granules are coated with graphite to protect the granule and to control the burn rate. The shape and coating is one way to control the burn rate of the powder. This is how you get faster burning powder and slower burning powder.

I am not as comfortable talking about the internal ballistics for a handgun compared to a rifle, but the principle is the same. A fast burning powder will promptly combust and generate its gas, but it will do so pretty much before the bullet has time to move much, if at all. You want the powder to burn quickly because the barrel is short and the bullet will not have the time to take advantage of the hot gases and accelerate as it would in a longer barrel. So you have to get this done quickly. Fast burning powders are usually associated with small charges such as in pistols. You want that small charge to turn into its gas right away.

On the other hand, in a large case inside a long barrel, you want the large quantity of powder to combust into gas at a slower rate over a longer period of time so that the pressure curve does not peak as quickly as with the fast powder but lasts a lot longer.

So for example, if you use one CM (cubic millimeter) of fast powder in a small case, you will generate the equivalent of 1000 CM of gas, but compressed in the same small case. In a larger case of say, 20 CM, you will generate 20,000 CM of gas, but this will not happen right away and the volume of the container will be much bigger. This is why you do not ever use pistol powder (fast powder) in a rifle case at the quantities usually associated with a rifle charge. Grain for grain, the amount of gas generated will be equivalent, but it’s all about timing in the release of this gas.

But in answer to your question, a proper amount of fast powder will reach its peak pressure faster in its proper application than an appropriate amount of a slower powder in its proper application.

So if your load is 5 grains of a fast powder in a pistol and you compare that to 50 grains of slow powder in a rifle, the fast powder will reach its peak faster than the slow powder. You have to use the appropriate powder for a given application.

This brings us to muzzle flash. This is caused by the hot pressurized gases coming into contact with the cool, low pressure atmosphere. If your firearm produces a huge muzzle flash that gives your buddy at the bench next to you a sunburn, just remember it is a sign that you are wasting all that energy. I have seen people just joyful at having a huge muzzle flash. On the line, I see all the competitors shooting hot loads (max and beyond) in their long barreled match rifles and one thing I notice is the total absence of muzzle flash. The hot pressurized gases are not wasted in our long match rifles.
 

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I'm still not getting the answer I'm looking for and maybe it is the way I'm asking the question. Let me try it with some made up numbers.

Lets say I'm shooting a 357 magnum in a 6 inch revolver. The pressure is 1000 psi with a fast powder with a complete burn in the 6 inch barrel and the bullet exits the muzzle at 1000 fps. Now if I take that same load and put it in a rifle with a 20 inch barrel, that bullet should exit the barrel at a slower speed (fps) because the fast powder peaked to soon and barrel drag slowed the bullet down in the longer barrel. However, if I use a slower powder in the rifle load, adjusted for the same peak pressure, would not a slower powder give me the same pressure except it would be on a longer curve (further down the barrel) and I get the same 1000 fps?

I'm aware that pressure can vary even in the same case, depending on bullet seating depth, crimp applied, case wall thickness, and a few other variables but I've always thought that velocity (fps) was a direct result of pressure. Am I wrong? Not being argumentative here, just trying to learn something.
 
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