is that correct?

Yes, if you are comparing the same weight charges.

At the risk of confusing the subject beyond belief...

with different charges things get complicated because of the progressive nature of some (actually most) propellants.

as pressure increases burn rate increases and as it burns faster the pressure increases and so on....

With ball powders the progressive nature is an artifact of retardants that have to burn off first, with "stick"
propellants it's a function of the sticks (which are hollow" burning from the inside out as well as the outside in and the surface area of the burn increases.

And this can be affected by the sie of the grains and the size of the hole.

Lastly with Alliant's "Reloader" stick propellants there is a chemical component (Nitroglycerine) not normally used in rifle propellants. that only starts burning rather late in the combustion cycle, but produces more gas than nitrocellulose alone...

So the "pressure" doesn't stay the same through the combustion cycle....

then things get really wacky when you consider that the movement of the bullet and the resulting increase in volume changes EVERYTHING


AD

Depends on which pressure you are referring to, i.e., where in the barrrel you are measuring it.

Chamber pressure MAY be higher with fast burning powders. depending on the amount of powder and where the measurement tool is in the chamber. Because the powder burns faster, more of it can burn before the gases from the start of the burn can get out of the way. That increases the amount of the gas in a given space, and so pressure is higher.


Still, in very small revolver cartridges very small charges of very fast powders may see pressures begin to fall rapidly even before the bullet leaves the cylinder.

Slower burning powders take longer to burn the same amount of powder, of course.

Obviously powder granule shape has a great deal to do with this. The greater the surface area available to be oxidized, the more rapoidly the powder oxidizes. But that also means that the rate of burn falls off more quickly as the surface area available to oxidation decreases faster.

With "progressive" burning powders, the intent is to make the powder burn both longer AND faster as the size of the combustion chamber increases (i.e., as the bullet moves down the bore).

So, many "slow" burning powders of modern design start OUT with low pressures, but as they burn, the pressures increase, or at least don't drop off anywhere as rapidly as do faster burning powders.

The result is, toward the muzzle end of the barrel, the pressures are actually much higher than with the faster burning powders.

Traditional ways of maintaining or increasing burn rate include using "tubular" longitudinal perforations in the powders, using heavy deterrant coatings, etc. The "tubes" increaxse in area as they burn from the inside out, the deterrent coating burns away and then leaves more easily oxidized surfaces exposed farther down the bore, and so on.

A classic example which helps us understand all this is the use of powders for the M-1 Garand. Powders from very fast to about as slow as IMR 4895 perform very well in the Garand. They get the bullet moving well, yet pressure has dropped appreciably by the time the bullet passes the gas port.

On the other hand, powders such as H-4831 generally perform poorly in the Garand. Bullets do not accelerate as well with 4831 as with 4895, BUT pressures as the bullet passes the gas port are STILL too high to be safe for the rifle's long term performance. The high port pressures eventually bend the op rod, which sends accuracy to hell in a hand-basket. It is even worse when folks add more powder than normal to get velocities up to the same level of acceleration as IMR 4895. Then gun operation may become so brisk that parts break.

Like everything else in handloading, it is sort of a "Yeh, but...." occasion. Firing of a cartridge creates a dynamic situation, and anything you can say at one point in the event may nor apply at every other point.

Mike,

This is one of those generalities that is generally true ... but is not the entire story in some situations.

Alberta Canuck's example is certainly a true one. Gas pressure as measured at the gas port can have quite an effect of the proper operation of auto rifles. They are usually designed for a specific pressure at the gas port. Garands and M14s and variants are designed for medium burn rate powders.

If I have a relatively moderately overbored chambering, the pressure peak for a slower powder will be lower than a faster powder but a slow powder may not burn entirely in the bore. Thus one can reach a situation in which increasing the charge weight of the slower powder will not always increase the velocity. Is usually accompanied by increasing muzzle flash. This is one clue that the burn rate of the powder being used is too slow.

Increasing the burn rate of the powder then causes the pressure to peak higher but also the pressure to be higher as the bullet goes down bore. In other words the pressure curve also broadens out.

quote:

Originally posted by Snowwolfe:
Yes, if you are comparing the same weight charges.

I'll throw in with that as a general rule. roger

I 'm guessing that what the original poster had in mind was start pressure, which as noted in at least one reply usually starts off high and decreases as the bullet moves out of the case. I would only add one thing to what I have read in the replies, but I think it might have some relevance to the question as pertains to safety and accuracy in rifle loads, and to a degree in pistol rounds.

The seating depth of your bullet affects the available volume of in the case for expansion of gasses. The bullet maker's manuals are the best source of information on the subject, of course. Still, it should be remembered that heavier bullets of the same caliber and general ogive type are going to be longer than lighter ones. Pressure falloff is going to be slower and in the case of a very tight chamber, changes in seating depth can definitely affect the performance of a cartridge.

This is one reason that BR shooters, and especially those who use jam seating work up the powder charge carefully. The initial pressures and amount of gas leakage around the bullet make a difference in the way the bullet enters and travels through the barrel. It's also why BR techniques and bullets are not reliably effective when trying to improve accuracy in factory (looser chambered) rifles. BR rifles are built to operate using higher start pressures.

It's undoubtedly rare that too deep a seating would alone cause a catastrophic failure, but it certainly could be a contributing factor. I've been told that in smaller caliber straight wall pistol rounds, a change of bluet seating depth is going to be a lot more critical than in something like a .30-06 round. A .001" seating depth change in a .32 acp is going to affect a lot bigger percentage of the available volume in the little case. Of course, the powder makers and bullet makers generally leave a large safety margin in their published data as far as pressures go. It is nevertheless foolish to exceed their recommendations, thinking they are being overcautious.

bluet? --- stupid spellchecker!

/

And I'd say, "No." A faster burn rate means just that, the powder burns faster. In the same cartridge (30-06 for example) 4895 will burn faster, that is release its energy more quickly, than 4831.

It is a mistake to think of the speed of the burn in terms of there being more pressure. The burn rate describes the energy release relative to time, not the total quantity of the energy released.

It is true that an equal weight of a fast powder will produce more energy (and pressure) than a slower powder. However, your statement doesn't on its face address the issue of quantity or weight of powder.

If one compares similar weights of powder, a faster powder (Bullseye for example) will produce more energy that a similar weight of 4350. This why more catastrophic failures occur because a reloader using a significantly faster powder than what he/she thought they were using, 47grains of 4227, in lieu of 4831, which would turn a 30-06 round (and rifle when fired) into a grenade.

Most careful reloaders see signs of pressure before they exceed the generous safety margins built into our firearms and recipes for loads contained in published reloading reloading manuals. Kudude

The VV manual has a couple of tables listing their powders in order of speed and gives an energy in joules/gram rateing to go with them. It doesn`t say much about it, and it appears to be small in variation, but it leads me to believe the amount of energy per charge may have as much to do with the peak pressure as speed, and definately does on the total amount of pressure on the bullet.

/

quote:

Originally posted by ALF:
...I was taken to task by Hotcore in another thread for claiming that velocity is a direct function of pressure ...

Absolutely, because alf was - WRONG AGAIN!!!

I asked alf to answer a few questions about his original post and he was unable to answer them. Since alf is simply "copying info from a book", that he obviously does not comprehend, it does make it difficult for him to answer any relatively simple question.
-----

As usual, alf has put enough in this post to confuse any of the Beginners who may be trying to understand the answers to the original question. Pitiful!

/

quote:

Lastly with Alliant's "Reloader" stick propellants there is a chemical component (Nitroglycerine) not normally used in rifle propellants.

But it is "normally" used in rifle propellants, all ball(spherical) powders are double base/nitrocellulose-nitroglycerine powders- quite a list of rifle powders to choose from, then there are some stick powders that have the "shit" and are triple based, nitrocellulose/nitroglycerine/nitroguanodine. Burn rates are established by a closed bomb test and listed by relative order of burn rate, therefore they can change position of speed by application- sometimes by as many as 4-5 places on the burn rate charts. .02

/

quote:

Originally posted by ALF:
Hotcore:

Exactly how did you come to our knowledge ? Suck it out of your thumb ?

If greater pressure is achieved with faster propellants ?, why do magnums require slow burning powders to give greater pressure peak curve in a retarded state of ignition ?

Curious Huh !.

Shoot Straight Know Your Target . ...

quote:

Originally posted by Alberta Canuck:
Depends on which pressure you are referring to, i.e., where in the barrrel you are measuring it.

I have seen that in Power Pistol vs AA#5.

Power Pistol pressure goes up very slowly as the powder charge is increased.[Pistol makes a big fire ball, but no change in brass]

AA#5 quickly gets high pressures as the powder charge is increased. [Primer falls out, case head blows off, etc.]

Yet most burn rate charts show AA#5 as slower that Power Pistol.

The only way I can figure that the charts make sense is that if AA#5 is slower at low pressures and Power Pistol is faster at low pressures.
And they used those two data points to make their chart.

Because I KNOW that AA#5 is much faster than Power Pistol at high pressures.

quote:

Originally posted by Hot Core:

quote:

Originally posted by ALF:
...I was taken to task by Hotcore in another thread for claiming that velocity is a direct function of pressure ...

Absolutely, because alf was - WRONG AGAIN!!!
...

Have you noticed how often chronographed pistol velocities are proportional to powder charge?
And yet the pressure goes up faster with the powder charge, and the area under the curve of pressure is directly related to velocity?

The more powder, the more energy available, but the energy of the bullet is proportional to the velocity squared.
This means that the efficiency is going up at a rate that [nearly perfectly] makes the velocity proportional to the powder charge and not to the square root of the powder charge.

That means the efficiency must be proportional to the root of the powder charge.
Why is that?

Hey Mike, As some have said, your original question is difficult to answer because there are many Variables involved. Depending on how a person perceives what you are trying to find out, it is possible to give you a correct answer, but that is incorrect with where you are trying to get to.

You have Peak Pressure, Sustained Pressure(the Area found inside the dv/dt curve) and the Duration of Burn. All are effected by the Dimensions of the Chamber, Bore and Bullets.

But, if you are asking which Powder(of equivalent amounts) will reach a MAX Pressure in a shorter amount of time, then the Faster Powder is the answer. It reaches the MAX Peak Pressure the quickest and also degrades inside the dv/dt curve the quickest.

That is why they taught us dv/dt in school, or perhaps I just like to think that is why they did.
-----

quote:

Originally posted by ALF:
...Unwilling or Unable to answer? or simply tired of your internet bullying of other posters on this forum.

Appears to be that alf is Unable to answer, for as long as I can remember. I believe I first noticed alf being Unable to answer the most basic questions concerning how Bullets actually perform on Game.

If by "bullying" you mean to imply that I tell a fool he is a fool, then that would be correct. I just post what is correct from actual first-hand experience rather than guess at it as the fools do. People can easily duplicate most of what I've seen if they just try.

Actually, I post much less now than I used to because of less fools on the Board. There was a recent Thread that a fellow named "HoldenV8"(I believe started) about Chronographs and not a single person tried to "weasel in" or "imply" that pressure could be told from the Velocity. The Board has come a long way to reach that Reloading Maturity level from not so long ago.

quote:

It seems that you percieve that you own the right to the topic of reloading

Once again - TOTALLY WRONG! This site is composed of some of the finest Reloaders currently alive. And mixed in with them are a bunch of Beginners who do not know who or what to trust in the threads. I do point out to the Beginners things I disagree with, and I can see where that is a HUGE problem for some posters. So yes, I do have the right to disagree with things I know to be WRONG! Tough cookies.

quote:

Exactly how did you come to our knowledge ? Suck it out of your thumb ?

This makes as much sense as anything else you post.

quote:

No maybe the word pitiful applies not to those who in a civil manner participate in this but to you who always loves to beat others down and demean others ???? Now that is pitiful !

Only the fools who desire to mislead the Beginners by making themselves "appear" to know more than they actually do. In fact, I could be wrong, but I believe I see more knowledgeable posters willing to come forward and disagree with those who are incorrect than used to. Granted some of them have a bit more tactful approach than I do (when dealing with fools).

Ye Gods, fellas....

Lets not get ourselves all confused by burn rates, etc.

Truth is, taking IMR powders as an example, several are the same basic chemical composition as each other, and with the same weight of charge, have the same amount of energy potentially available for release.

Burn rate does not increase or decrease the amount of energy available. What it does do is change the CHAMBER PRESSURES created, by determining how quickly the energy is released.

Let's create an imaginary energy unit called a "demi-framis", and stipulate that every gram of a series of powders (A, B, & C) contains 100,000 demi-framises of energy.

Powder A burns so quickly, all 100,000 demi-framises are released before the bullet can even leave a 2" long cartridge case. That means the cartridge case itself determines the length of the combustion chamber, i.e., 2" long.

Powder "B" burns with a speed that allows all of the powder's 100,000 demi-framises of energy to be released by the time the bullet has traveled 2" down the bore. That means the size of the combustion chamber is 4" long (2" of case and 2" of bore), or somewhere just less than twice the effective size "combustion chamber" of the same rifle using powder "A".

Then, let's say Powder "C", a progressive burning powder of the best class, burns at a rate that releases all its 100,00 demi-framises of energy by about the time the bullet is 6" down the bore. That combustion chamber is effectively 8" long (2" of cartridge case, and 6" of bore).

Given a similar charge of powder, which one will produce the highest pressure with the same weight of both powder AND bullet? It will probably be the one which releases all 100,000 demi-framises of energy in the SMALLEST combustion chamber or pressure vessel, won't it? That's Powder "A".

Corallary to that, as soon as pressure quits increasing, it begins decreasing (the bullet is moving and increasing the size of the pressure vessel). So, which one quits producing pressure and has pressure start to drop first? Again, Powder "A".

That powder stands a good chance of having the LOWEST pressure at the muzzle end of the bore.

I'm tempted to ask, "That ain't rocket science is it?", but I don't intend to be insulting to anyone...just to clarify if I can a bit of what we are all trying to describe.

Thinking about the above shows the advantage of large combustion chambers (cartridges) in producing magnum velocities. If we can use enough of Powder C to get up to the same peak pressure of Powder A, we will have the same height of propelling pressure for a longer burn time...i.e., we will be able to release 200,000 or even 1,000,000 demi-framises of energy behind our bullet without blowing the rifle up.

And that's why we use more of a slower burning powder in large magnum cartridges.

Magnificently done, AC!! roger

quote:

Originally posted by swheeler:

quote:

Lastly with Alliant's "Reloader" stick propellants there is a chemical component (Nitroglycerine) not normally used in rifle propellants.

But it is "normally" used in rifle propellants, all ball(spherical) powders are double base/nitrocellulose-nitroglycerine powders- quite a list of rifle powders to choose from, then there are some stick powders that have the "shit" and are triple based, nitrocellulose/nitroglycerine/nitroguanodine. Burn rates are established by a closed bomb test and listed by relative order of burn rate, therefore they can change position of speed by application- sometimes by as many as 4-5 places on the burn rate charts. .02

I was only trying to illustrate the fact that differing composition had an effect on initial burn rate rate AND energy content above and beyond the factor of "Fast" or "slow"

Let's be honest a given weight of pure nitrocellulose doesn't have as much energy
as a propellant that's 10% nitroglycerine by weight. or 20% by weight...

The Nitroglycerine content of the various alliant propellants is what makes them somewhat "special", unfortunatly it also tends to make them burn "dirty".

It has been my understanding that nitroguanidine
(you spelled it wrong is used in artillery propellants and is mostly added as a flash supressant.

Am I wrong?

I don't think so.... All that being said I LOVE A-C's post

And DAMN!!! I was worried about making the discussion "complicated" silly me....

AD

quote:

Originally posted by Dr.K:
"in a retarded state of ignition"
Shoot Straight Know Your Target . ...

That pretty much summs up this entire post!!

I've got a headache!

Bill

Great post, AC

Restated. ..
pressure has very little to do with MV, rather the area under the pressure curve (work) will.

Mike, faster powders can lead to higher pressure, but there's lots of variables, and if the max working pressure is 65,000psi, you are trying to find the best "work" powder, which is why reloading manuals always have a faster load in any given chambering.... because thats the "right" amount of work

Mike, loosely speaking "yes" but technically "no." "No" because "burn rate" is not a technically correct term.

Relative burn rates are established either in specific lab tests or by comparing relative charge weights across different cartridges. Not all cartridges and chambers will follow such trends. Cartridge pressure limits have an effect because pressure affects the instantaneous rate at which gases are produced ("burning"). Bullet engraving forces may cause the burn to quicken because the bullet didn't get out of the way fast enough, thus raising pressure and thus gas production. The relative size of the bore to the case capacity will affect how fast pressure is relieved by a given bullet acceleration, and this in turn will affect how big the grains are (and thus affect gas production) when a certain pressure is reached.

The list goes on. You simply cannot depend on a "burn rate chart."

quote:

It has been my understanding that nitroguanidine
(you spelled it wrong

Holly bat-shit(guano) thanks for correcting my spelling for me! Did you learn anything when you looked it up on the internet?

I was only poking a little fun , because there are many variables .

As posted by so many of you . Retarded ignition is from heavy graphite it delays burn time for pressure build also as a side benefit anti static coating .

Great Post AC also jeffeosso ,Allan DeGroot.

Your right bartsche ; Whiskey cost money !.

Det cord burns 7 times quicker that 80% nitro .

Nitro goes BOOM Det Cord goes CRACK / Similar to the difference in sound a 50 cal black powder muzzle loader makes as opposed to a 22-250 or .223 .

I cannot recall the amount of noise that 587K pounds of 80% Nitro 2X16" Hercules commercial sticks coupled with Anfo Prill made on a single blast . I can how ever vividly recall the mountain moving 5.7 Ft. East ward .

A right of way shot for Feather River aqueduct pipe line Ages ago !.

Welcome to my work introduction too drilling & blasting Dams ,bridges, pipe lines , rock quarry's , pit mines , housing pads , Freeways . Only later to be recruited by Uncle Sammy for an Asian Adventure !.

Here I thought only Ft. Sill & Ft. Polk were Arm pits of the World was indeed VERY FOOLISH OF this BOY !!!.

Shoot Straight Know Your Target . ...

/

Given the same gun, case, bullet and varying amounts of the same powder, velocity depends on induced pressure. The fact that a point of diminishing return is reached, does not make the basic premise invalid. In fact that is a sign that must be seen as ballistic limit which should not be exceeded. Pressure testing in a lab can confrm this as a senseless endeavour.

Warrior

Would you folks mind talking a little slower here please? I am getting a headache already!

Did someone mention that peak chamber pressure does not occur until the bullet has moved a fair distance down the bore?

I have a question of my own I would like to add to Mike_Dettorre's question, if I may, Mike? How does compressing the charge influence burn rates/pressure curves/peak pressures? This question arises from my hornet loads with Lil’Gun. The powder charge comes halfway up the neck and gest compressed to the base of the neck - a very long neck in comparison to the case volume. So much so, the powder is very difficult to 'dig' out of the case again.

Thanks.

Pssst……… Al. You spelt “supressant†wrong! Just kidding!

Allen, please would you clarify, I always used to think that the nitro-glycerine was the fast burning component (and therefore burned first)? My understanding was that pure nitro-glycerine was so sensitive, just a tap on the container could set it off?

Thanks

quote:

Originally posted by ALF:
.....pressure has very little to do with MV, rather the area under the pressure curve (work) will.......

That statement is correct. "area under the pressure curve" is the MEAN pressure. Muzzle energy will be proportional to mean pressure and bullet base area. The velocity will then be proportional to the square root of the muzzle energy. Heat and ejecta kinetic energy losses kinda ruin the powder charge to velocity curve a bit.

quote:

Originally posted by 303Guy:
Pssst……… Al. You spelt “supressant†wrong! Just kidding!

Allen, please would you clarify, I always used to think that the nitro-glycerine was the fast burning component (and therefore burned first)? My understanding was that pure nitro-glycerine was so sensitive, just a tap on the container could set it off?

Thanks

Hi again, 303 Guy. I am obviously not Alf, but will essay a response anyhow.

Yes, pure nitroglycerine was added to original double based powders, and still is to some. For several chapters on powder-making, including nitroglycerine enhanced nitrocellulose powders, I recommend Phil Sharpe's book "The Complete Guide to Handloading.

It is not the best book out there, but it is probably the most available that addresses how powders were (are) made. It was published originally in 1935 and updated in 1947 to cover the new IMR and Hercules powders to that time, and the manufacture of the then-new ball powders.

Pure nitroglycerine is indeed sensitive...enough so that most nitro powder factories manufacture their own nitro on site rather than risk (and pay the costs of) shipping it.

Having said that, do you recall what made Alfred Nobel his fortune? His invention, "dynamite", is pure nitroclycerin absorbed by a non-explosive base, such as diatomaceous earth (ingredients have been modernized since then).

That makes it CONSIDERABLY more safe....insensitive enough that it takes a blasting cap to reliably and predictably explode it. So it is with it absorbed in nitrocellulose, where it takes a primer to fire it.


(BTW, dynamite is one of those compounds which is both explosive (detonates under certain conditions) and burnable. It burns rather slowly in small amounts, without usually exploading. However in larger amounts, the heat and energy of the deflagration may cause it to detonate too.)

quote:

Originally posted by Alberta Canuck:
It burns rather slowly in small amounts, without usually exploading. However in larger amounts, the heat and energy of the deflagration may cause it to detonate too.)

Had to dispose of over 3/4 of a case in a wooden crate dated 1943. This was in 1970 and was in a shallow wind cave against a cliff with us on a bench 300 ft.above the Colorado River near the Utah border.

Around the crate was a bunch of solid crystal of near white to green in color that had ooozzed out of the case. We had been sent out to get rid of it by the Mesa county sherrif. We were tempted to back off about 50 yds. and shoot it but could see possibly being blown off the bench into the river or getting buried in a rock slide.

We stripped a bunch of bark from some old cedars and CAREFULLY piled it on the dynOmite. We started it burning and than ran as far from it as we could( about 35 to 50 yds.) and got to huging the earth behind a boulder.

That was one of the hotest fires we ever saw. Rocks started splintering and falling and right there we just knew we were in deep shit. The fire seemed to last for ever but in reality probably less than 2 min.Talk about 2 wobbly leg guys walking out. roger

Originally they used saw dust not diatomaceous earth.

quote:

Originally posted by bartsche:

Originally they used saw dust not diatomaceous earth.

Roger-

Here is the original patent application filed by Alfred Nobel himself:

http://www.dprix.com/biblio/nobel/nobel.html



This is a good read, as it includes the ingredients of dynamite, why easily compressed media such as charcoal (or sawdust) should NOT be used, what the purpose of the invention is, how to explode it, how to make it, and various other relevant items of interest, all from the pen of the inventor.


It is my understanding that the nitroglycerine burns neither before nor after the nitrocellulose in a double-based smokeless gunpowder. In fact it is part and parcel of the powder, is an integral part all the way through the powder, and burns as part of it.

Pure nitrocellulose, until gelatinized in powder manufacture, is kept wet (using water, alcohol, ether, or some other wetting agent) until made into "powder". If it is not kept wet, it tends to spontaneously combust, and spontaneous nitrocellulose fires were a daily occasion at early smokeless powder factories (through at least the 1940's).

quote:

Originally posted by Alberta Canuck:

quote:

Originally posted by bartsche:

Originally they used saw dust not diatomaceous earth.

Roger-

Here is the original patent application filed by Alfred Nobel himself:

http://www.dprix.com/biblio/nobel/nobel.html

I am surprised and I stand corrected. I've been carrying that information in my brain since school days over 50 years ago. roger

Don't feel the least bit embarassed or sheepish, Roger, your tiny bit of long-ago learned misinformation is very understandable.

As we all know, dynamite was a huge, immediate, success and quickly moved from use in mining, to other uses in excavation, cess-pool "rejuvenation", tree-stump removal, road-building and tunneling, bombmaking, as an experimental propellant in naval guns, and so on.

Naturally, everyone wanted a piece of that very lucrative pie. So, folks began mixing nitroglycerine with darned near everything that would absorb any of it, patenting their mixtures, and claiming all kinds of wonderous advantages for THEIR particular combinations.

Perhaps even the majority of those "quasi-dynamite" mixtures were patented and made in the U.S. They certainly were common here. So, it is very, very, possible that some form of sawdust/nitroglycerine variant was made and sold here, then disappeared.

Anyway, I'm always glad to hear your input. I think you are a good man and a clear thinker.

AC

quote:

Originally posted by ALF:
The logic alludes me ?

"Restated. ..
pressure has very little to do with MV, rather the area under the pressure curve (work) will."

This is a contradiction in itself???

Pressure applied over time = Specific Impulse or SI = the area under the pressure time curve.

It is pressure applied over time that imparts velocity to a bullet with specific sectional density.

The units of measurement of the SI and the velocity x Sectional density are one and the same.

So Pressure has everything to do with velocity, it is the very essence of propulsion of a bullet in a modern gun / Rifle.

The inherent quickness of the powder, its burn rate as determined by amongst other things shape, composition and the addition of retardants , the mass of powder actually consumed during the combustion process and the potential energy per unit mass of powder within a closed or vented chamber of certain volume is what gives the Pressure time curve it's spatial configuration.

Alf, Alf what are you trying to do here? It sounds like from the posts that you are trying to explain a principle to Hot Sh$t. I would think by now that you have learned that Hotsh$t is impossible to reason with or explain to because after all and as said before "HE IS THE SUPPOSITORY OF ALL RELOADING KNOWLEDGE" If you doubt that statement ask him and he may even confirm it.

I have him on my ignore list and it's wonderful.

Trying to confuse him with physics, chemistry, or any other applied science or your own experience is foolish and I even heard he tried to explain politics, Pitiful!!!!

Seems like he suffers from some mental challenges perhaps fostered in the hills of Kentucky. Place him on ignore and share your knowledge and experience with those whose are interested in your input. Nobody cares what he thinks.