Cylinder Pressure

[Leftoverdj]

A recent series of posts on an inappropriate thread produced a request that I start this thread. I believe a fundamental misconception was involved. The original claim was that it took about 10, 000 psi to dislodge a bullet from a case. When an ingenuous poster showed that took less than 200 psi to dislodge a bullet, the claim was amended to " by the time the bullet seperates from the case, 10,000 PSI or less of gas pressure has developed from combustion.
...

The point of all this is to show that peak pressure can not take place at the cylinder of a revolver and understanding peak pressure and pressure curves will help to make a more informed choice on powder selection in regard to barrel length. "

The misconception is pressure within the cartridge corresponds to pressure within the cylinder. With a powder that does not completely consume within the case and a properly fitted bullet, the pressure curve within the cylinder will continue at least until the base of the bullet clears the front of the cylinder. As internal ballistics go, sufficient time elapses for a considerable increase in pressure after the bullet leaves the case.

[Leftoverdj]

No comments?

[redhawk41]

what i understand is this (numbers are arbitrary):

it takes .01 seconds for the bullet to be unseated, due to friction and momentum.

in this .01 seconds powder combustion generates 10,000 psi of pressure.

it does not actually take 10,000 psi of pressure to unseat the bullet. a primer can unseat a bullet. if it did take 10,000 psi, i'm not sure i would be capable of operating my kinetic puller.

what i am trying to understand is this:

in a revolver there is a huge (relatively speaking) gap between cylinder and bore. it seems to me that any pressure developed after the bullet jumped this gap would be less effective because it would seek the path of least resistance out the cylinder gap.

it seems to me that peak pressure must occur in the cylinder in for maximum force transfer to the projectile.

[mandark]

No the gap is not huge for the properties of propellant gasses. Try and think of the combustion by-product (plasma) as water. It has a mass itself that that will want to follow certain rules of flow mechanics resisting directional changes. This plasma also has viscosity and the gap is only a relief for a small percentage of total volume of gasses produced by combustion as compared to the increasing volume of space in the bore behind the bullet traveling down the barrel.

[brickeyee]

For a typical revolver round the spread of powders runs a wide enough range to produce complete powder combustion before the bullet has cleared the case (Bullseye) to a significant portion still burning in the barrel (H110).
you can easily play around with Quickload and see what time and distance to peak pressure are even for combinations that would be very foolish to try (like a .44 mag full of bullseye).

[drinks]

Brick;
If bullseye is completely consumed in the case, how does the plume of fire come out the muzzle on a 5 1/2" .45acp in a darkened room?
Don

[smokin54]

and then why would my 10 inch 454 develop more velocity than my 4 3/4 inch version ? There is still pressure accelerating the bullet or the friction would be slowing it down . Is that simple enough ?

[brickeyee]

Smokeless powder 'burns' by decomposition to simpler molecules, not by oxidation. There is not enough oxygen present (or other oxidizer) to react with the simple molecules by oxidation (and this reaction is to slow anyway). The flash is the hot products of the smokeless powder oxidizing using the atmospheric oxygen (notice that the reaction is slow enough to easily be seen and create the fireball). There are additives that can help reduce the flash by trying to speed up the straight oxidation reaction, but the reaction time is limited by the barrel time of the projectile. Adding these chemicals also takes up space and lowers the energy density of the propellant. This is not a problem for most fast powders that are rarely used in case filing quantities, but can be an issue for slower rifle type propellants.
Adding nitroglycerin to create a double base powder tends to make flash worse since it is inherently an underoxidized compound (does not contain enough oxidizer to take all the atoms present to complete combustion).

[Leftoverdj]

"and then why would my 10 inch 454 develop more velocity than my 4 3/4 inch version ? There is still pressure accelerating the bullet or the friction would be slowing it down . Is that simple enough ?"

Smokin, there is indeed pressure, but I don't claim to know how much. The pressure when the bullet exists the 10" barrel could be much less than it was at the 4 3/4" inch mark and the velocity would still be higher because even the reduced pressure levels were sufficient of continue to accelerate the bullet.

[Sturm]

The Ingenious and very well meaning poster that conducted his test was using air pressure (pneumatic) which is applying a constant force on the bullet and even he recognized the invalidity of this in comparison to gas pressure from combustion of smokeless powder. Are you saying you still don't get it?

I have taken some heat from several posters on this forum for stating nothing more than the results conducted by the physiscists of H.P.White laboratories and the evidence exists in the Lyman reloading manual. At least it does in the 46th edition.

If peak pressure occured in the cylinder there would be much less difference in performance between the faster and slower burning pistol powders while a bullet is traveling through the same distance of bore and rifling. H.P. White labs concluded that 10,000 PSI of gas (FROM COMBUSTION NOT PNEUMATIC) pressure is what is necessary to seperate the bullet from the case. Since this takes place in Nano or Pico-Seconds, I would like to see someone explain their "theory" on why a cartridge that will develop 40,000-50,000 PSI of average peak pressure (or more in the case of the .454 Casull) while the powder continues to burn while the bullet travels down the bore, could possibly think that peak pressure occurs at the cylinder. Might be easier if they just stick to using W-231 in magnum revolver cartridges. You won't catch me doing either! I think most of us that are experienced understand this.

Some reloaders are just not aware that the differences in burn rate and pressure peak can affect the peformance and velocity of different Magnum Revolver or any cartridge for that matter. Take the common magnums: Blue Dot at maximum pressure (original spec) will give velocity as high as any powder in the .357 Magnum. For evidence, consult a load manual that listed data with the original maximum pressure spec's of these cartridges rather than the current 35,000, or 36,000 PSI data which is still in use, but has been recently updated for the .41 and .44 Magnum to 40,000 C.U.P. or approx. 45,000 PSI. BTW W-296 and H-110 operate at this level (35,000 PSI) or less in the MagnumRevolver cartridges we are talking about. I'm pretty sure there is a majority here that believe that Accurate #9 performs better than H-110, or W-296 in the .41 magnum. Why is that? Well I'll tell you. The pressure requirements of the .357, .41 and .44 magnums are different. Different diameters, different weights, and different case capacities. You can't put enough H-110 or W-296 in a .41 magnum case to match the higher pressure peak of Accurate #9. Shorten the barrel length and you will need a slightly faster powder to achieve maximum peak and one reason why you see me recommending AA#7, Blue Dot, VV 3N37 and N-350 and even HS-6 for 3 and 4" magnum revolvers. Unless you want incomplete powder burn, or unecessary levels of muzzle blast.

Still don't get it? Try taking a .270 case with Jack O'Conners favored load of H-4831 and a 130 gr. Spitzer and firing it in a 24" barrelled Ruger 77. Now if you decide to hunt with the Ruger 77 with a 20" barrel, are you still going to use that same H-4831 load? or will you more appropriately change your powder to IMR or H-4350 or something slightly faster? People think that physics change from Rifle vs.Handgun reloading, yet many principles are the same or similar when it comes to pressure peaks or selecting the appropriate powder in burn rate to suit the specific needs of the individual cartridge or firearm. Even the uniformity of ballistics for higher load density. Handgun or Rifle! Or you could just use Titegroup, W-231, or Unique for all handgun loads! And, some reloaders do!

I don't need to yell or type in extremely bold text to prove my understanding or lack thereof when it comes to physics. It is a constant science that speaks for itself. If you don't even understand the difference between combustion and pneumatic pressure, I suggest you Bone-Up!

[Unclenick]

I think Sturm is right. Life is too short to drink cheap beer. As a card-carrying member of the AHA, I can vouchsafe this statement.

To the less clear things, Harold Vaughn's book, Rifle Accuracy Facts, also shows measurements indicating bullet movement is apparent after about 10,000 PSI is reached in a chamber of combusting propellant. Does it take 10,000 PSI to remove a bullet from a case? No. Not if you take your time. Does it take 10,000 PSI to remove a bullet from a case really, really fast? Yes. Just as it takes more horsepower to take your car from 0-60 in a short time than it does to get it there gradually. Acceleration equals force divided by mass.

Will a powder continue to raise chamber pressure even after a bullet clears the case neck? The right one sure can. Even a barrel-to-cylinder gap has laminar fluid flow resistance too great to relieve pressure as fast as the right powder generates it.

Do pneumatic pressure curves resemble powder curves? They can. You see this in spring piston air guns where the pressure starts to build as the spring compresses and the pellet starts to move, then the pressure peaks as the spring slams home and begins to drop as the pellet progresses forward, creating increasing volume for the fixed mass of gas to fill. Boyle’s Law. Can it behave very differently? Sure, just feed the pressure from a large pressure vessel through tubing significantly larger than the bore, and it will pretty much seem like the pressure is constant. Not quite, but pretty much. A pneumatic air gun is at the other extreme, applying full pressure as fast as the small reservoir can get it through the valve, dropping down from there as the pellet expands the volume it must fill. How to tell what's really happening in your specific case? Get an Oehler model 43 ballistics lab and some strain gauges and a computer and have at it.

As to revolvers and pressures in general, work your loads up slowly and watch for pressure signs, just like any other reloading. Increasingly flattened primers or cases that stick in the cylinder on extraction are bad mojo in a revolver. Do not fire more of that load. Please back off the charge so we don’t get a tragedy to talk about on the board.

Nick

[Sturm]

Unclenick, OUTSTANDING! Very well defined examples. Since their are a few cartridges that don't get beyond 10,000 PSI, the slow accelleration case example is definitely noteworthy, it just hasn't been a focus of the Big Bang Big Magnum discussion. But, for shooters that love low velocity target loads in their .32, .38's, .44 Sp. etc.... it is entirely relevant and appreciated. Look forward to more of your posts! If I haven't said WELCOME before, I certainly do now. The timing was impeccable BTW, the slogan is Wersteiners! I will say that the new Bud Select is very much to my liking. Any chance that it is the original Busch BAVARIAN?

Mandark, I agree. The pressure rise is most definitely linear on the vast majority. The Only way a powder could reach peak pressure in the cylinder would be with the very fastest burners like Norma R-1 (the fastest smokeless powder in existence today) operating at a pressure that would peak so quick that it would not exceed the max operating pressure of the load itself. Still, not very likely. While computer programs may allow you to play with peak pressure and pressure curves, when one will accurately show an exact pressure curve for the specific load you develop, I'll buy it. Otherwise it is sophisticated Gaming!

[brickeyee]

Since I happen to have the .45 ACP number handy, I ran a 15.5 gr load of H110 behind a 230 gr FMJ. Time to peak pressure is 0.192 milliseconds, and bullet travel at that point is 0.25 in. The bullet has not cleared the case.
If I get a chance I will run some other calibers (I have to go find some bullets to measure length for the seating depth portion of the input data).

There is a larger issue with using what are essentially static pressures to determine the behavour of firearms metals. While the pressure vessel equations are well understood, the response of materials to very fast pressure transients (typical of firearms) is not well documented.
The measurments require both strain gauge and piezo pressure be measured at the exact same time. Only then can the material response be derived. I participated in some experimants in this area (as an EE I provided the instrumentation) and a lot of materials guys saw things they did not understand and that did not agree with the standard pressure vessel (static) stress-strain curves. There is still limited research in this area being performed, but like most other things money is limited.

[Sturm]

Brickeyee, read the first part (or all of it) of Unclenicks post again. This discussion is much more relevant to the discussion of higher pressure cartridges than the slow .45 ACP which you have slowed even further with a powder too slow for the .45 ACP. I don't dispute your finding, but try again with say a 10mm with a 170 gr, bullet at 1300 FPS. Or, max loads of .357,.41, .44, .480 Magnums or the .454 Casull. I think Unclenick accurately describe the change in parameters with slow accelerating cartidges. An 1150 FPS 185 gr. +P might show you what I mean, but it is still reletively slow in comparison as far as a pressure peak at an operating pressure of around 20,000 PSI.

P.S. Forget the H-110, unless you really do load it in the .45 ACP, you are only slowing the process further and confusing your own investigation. What is it it you .45 guys like so much? W-231, HP-38, AA#2, AA#5 VV N-320 and even Unique will give you a much better result. Hypothetically or otherwise.

[Leftoverdj]

" (B)y the time the bullet seperates from the case, 10,000 PSI or less of gas pressure has developed from combustion." is not the same statement as "H.P. White labs concluded that 10,000 PSI of gas (FROM COMBUSTION NOT PNEUMATIC) pressure is what is necessary to seperate the bullet from the case." Same poster has made both statements and seems to believe that they are interchangeable, They are not.

No one has yet chosen to address the fact the cylinder is still sealed after the bullet has left the case and until the bullet exits the chamber. That time may be milliseconds, but it is still sufficient for pressure to increase markedly, depending on the powder used.

Y'all wanna argue about something else, go right ahead, but those are the two points I started this thread to address.

[WESHOOT2]

I think AA9 is more accurate through my 41, but H110 definitely sends bullets out faster.
5.5" Redhawk.

Oh, and a pat on the back for clear thinkers........

[Sturm]

WS2, how much faster in comparison to the degradation of accuracy? I have not seen any load data where H-110 gives faster velocity than AA#9 with max charges. Maybe you can provide some real world data!


LODJ, I don't disagree with your contention here, but when we get to the Magnums and not the .45 ACP with H-110, I also think we will get back to a better real-time perspective than .192 Milliseconds better defined as 192 micro-seconds. You keep saying what H.P. White is not saying even though anyone can see for themselves in the Lyman manual, so why don't you tell us what they are saying if you are getting a different interpretation. The reason I asked you to start a thread to begin with is that you had a disagreement, but no explanation to your counter. Unclenick has also cited another reference that concurs with the H.P. White conclusion as it relates to the topic which we started with when you made the disagreement. That of the .41 Magnum, Remember? or do you want to have another debate on how much the less than 10,000 PSI we are talking about with the .41 Magnum since we have seen it demonstrated already that there are exceptions with slow accelerating cartridges that were never a part of why you started this! I can tell you this, H.P. White did conclude that pressure peak occurs well into the bore and that distance is determined by the burn rate and pressure peak of the load.

BTW, for those who don't know and are following this, H.P. White laboratories is one of the premier ballistic testing labs in the U.S. FYI.

[Leftoverdj]

Sturm, I dunno what HP White said. All I know is what you claimed it said. Since you have given three conflicting versions, I am a mite confused.

If you would care to post exactly what HP White said rather than your opinion(s) of they said, we'll have something to talk about.

[Sturm]

Do you not have a Lyman Manual? I agree you are a mite confused because if I was going to tell some one they were mistaken, I would at least first have an understanding of why, or at least look at the evidence shown IN PRINT. I don't get on here just to disagree, in fact I receive a number of PM's from reloaders who genuinely want some help. Some long time posters here seem to want to do nothing more than carry a status based on the number of posts they have generated. This will do NOTHING for a reloader in search of help or expanded knowledge. Guys get on here and and discount burn rate charts and pressure curves, when, if they are understood can help the reloader significantly with proper powder selection, instead of believing you use magnum powders for magnum revolvers and W-231 and Unique for everything else in handgun reloading. Kind of like the thread on 30-30 reloading where you suggest that W-748 and H-335 are the same powder or not a dimes worth of difference. WeShoot2 said that H-110 gives higher velocity in his 5.5" Redhawk. Well it don't in mine so SHOW ME THE DATA! H-110 is slower and requires more barrel length to develop max velocity than AA#9 in the .41 Magnum. While we're at it, where's Mike Irwin, since you three like to ride the same wagon?

I'm not going to put up the article from the Lyman manual entitled: A Limited Comparison of the Crusher and Piezo Systems, because YOU and a couple of the other guys from the .41 magnum debate SHOULD HAVE ALREADY READ IT BY NOW! Maybe you were too busy posting!

[Mike Irwin]

"instead of believing you use magnum powders for magnum revolvers and W-231 and Unique for everything else in handgun reloading."

As opposed to running in circles screeching that 231 is "inappropriate" or "not approptiate" for loading lower powered loads in magnum cartridges, or whatever such stupidity you came across with?

You're right, that's eally helpful, and you're to be *cough* congratulated for the furtherment of *cough* knowledge.

Not everyone is looking for magnum loads in their magnums for every application.


"Some long time posters here seem to want to do nothing more than carry a status based on the number of posts they have generated."

Ah, you're still on that.

Gee, could the fact that I have 12,000+ posts be a factor of something else entirely, something that you've not yet comprehended?

The fact that I've been posting here for going on 6 years? As opposed to your what, 2 months?

Nah, obviously not.

[Sturm]

You throw the term stupidity at me, so let me tell you what I really think Mr. Lee die advocate. Buster, your the epitome of stupid! You are not only arrogant and insulting, you are also one of the most insecure people I have encountered on the gun forums. Like your comment in the .41 magnum thread "I was the first here to recommend Accurate #7", funny, I had previous to that brought it up again because you were again recommending W-231 and this time for the .41 Magnum. I find this amusing, because in the 2 months I have been here I don't recall you recommending #7 when I arrived. Maybe your learning. But, I doubt it. And I don't bash W-231 to those who use it in the .45 ACP, because I think that is the best application for it. Not Magnum rounds where we both know you have recommended it. If you want to shoot light target loads, why not just shoot them in a .38, .41, or .44 special and yea, there is a .41 special, but it will require you to excercise your hands and brain at the same time. Might be pretty heavy lifting in your case.

Almost 13000 posts must mean that you think someone gives a sh**. The only reason I ever responded to your post was because you were praising and recommending Lee Dies, and you have had a burr in your ass ever since, for those that wonder what the basis for all this BS is about. You like to be a smartass, but very little of your information, except your database of S&W dates of manufacture could be considered intelligent. Mr. Longtime shooter and reloader, my credentials will go toe-to-toe with yours any day of the week and I don't have to walk around pissed because I am a walking, talking contridiction in my own state! Say hello to Dianne for me with a one finger salute and tell her I said thanks for staying out of TEXAS!

One thing 13000 posts is good for here is that even though you want to throw insults, I will most likely be the one that has threadlock after his last post. If it's not post delete. Everything else, I'll leave to my peers, of which, you don't even rate!

[Mike Irwin]

"Mr. Lee die advocate"

Check. As I've said before, and I'll say again, not every reloader needs to spend upwards $100, or more, for a set of dies. Not every reloading wants, or needs, to spend that kind of money to make not only servicable, but also accurate, ammunition.

"You are not only arrogant and insulting"

Check.

"you are also one of the most insecure people I have encountered on the gun forums"

Uncheck. Perfectly secure, and not afraid to make my opinions, or counter opinions, know, or call BS on others whose opinions I find to be... lacking.

"Like your comment in the .41 magnum thread "I was the first here to recommend Accurate #7", funny, because in the 2 months I have been here I don't recall you recommending #7 when I arrived [what, you don't think there was life before you? If not, how did I ever accumulate 13,000 posts, then?]."

First reply in this thread - http://thefiringline.com/forums/show...light=accurate

I was referring to that thread, and that thread alone when I said I was the first to recommend AA 7, but since you do raise the question...

First reply in this thread... http://thefiringline.com/forums/show...light=accurate

Looks like most of my recommendations to use Accurate Arms powders were in another forum, though.

"And I don't bash W-231 to those who use it in the .45 ACP, because I think that is the best application for it." You do realize that you can double charge a .45 with 231, correct? Since that seems to be your major gripe against it when used in magnum cases, one must wonder why you'd recommend it in the .45.

"Not Magnum rounds where we both know you have recommended it." Yes, yes I have recommended 231 in Magnum CASES, not Magnum ROUNDS, there's a difference, as I've pointed out by noting that 231 is at the bottom end of the loading spectrum for the .41 Mag, and doesn't get anywhere near full power loads. You'll also see that I've recommend it for quite a few other cartridges, as well, including .45, .38 Spl., .32 Long, and .44 Special (althought I'm not a great fan of it in that cartridge in my gun). "Magnum" is a name, a trademark, a frame of mind, a potential. It's not an absolute.

"Almost 13000 posts must mean that you think someone gives a sh**." And that begs the question as to why you're here, then? You must think someone... care to finish the sentence?

"because I am a walking, talking contridiction in my own state!" Contradiction? Please be so kind to point where where I contradict myself.

"I'll leave that to my peers, of which, you don't even rate!" Now who's being insulting? Sort of contradicts your holier-than-thou screed, don't you think?

"I will most likely the one that has threadlock after his last post." If that would make you happy. I will remind you, though, that you invoked me here, not the other way around.

Oh, and just for the record? I don't recommend Unique for anything other than shotshell loads.

[Mike Irwin]

Hurry hurry, Strum, times wasting...

[Sturm]

I think reading the locked .41 magnum thread will tell all what started all of this BS. I did not invoke you, I said that you, WeShoot2 and LeftoverDJ like to ride the same wagon, well at least you did on the .41 magnum thread. I did like the point about the use of W-231 in Magnum cases not having to be Magnum level. Hell, I almost feel the same way except that i wouldn't use it in a magnum case to start with when there are so many choices that are better suited, yep, that includes Unique, but i don't use it either. By the way, I don't and never have spent $100 for a good set of dies. REDDING Titanium carbide is a little more expensive, but gees, is it so hard to comprehend why. Know anything about machining Titanium? Spend half the money and believe you are getting a die set that's just as good. Maybe you need to be reminded of P.T. Barnums favorite quote. remember that one? Ever seen REDDING issue a recall on their dies? So here is my final thought! Quack, Quack, Quack!

[Mike Irwin]

"Spend half the money and believe you are getting a die set that's just as good."

Just as good. Really? I'd ask you to point out where I ever claimed that Lee dies are "just as good."

I'll call BS on that comment right now and save you the trouble of having to look. I've never claimed it.

What I HAVE claimed, however, is that Lee dies work, and work well.

Will they give the highest levels of precision, the kind that's sought after by competitive shooters?

"I did not invoke you, I said that you, WeShoot2 and LeftoverDJ like to ride the same wagon..."

You never invoked me?

"While we're at it, where's Mike Irwin..."

You called, I came.


Oh, and seeing how you like to keep invoking the Lyman manual, a few thoughts from Lyman 47...

"Some reloaders have good reason not to want the highest possible velocity from a specific bullet weight. A desire for recoil reduction, or the use of a very powerful cartridge on light game are just two reasons that a powder might be selected from those that are not the "best choices". [Note their terminology, as opposed to the claim of 'inappropriate.']

I've said it before, and I'll say it again... Inappropriate is different from less that optimal, as pointed out by the passage above.

If a power is inappropriate for a cartridge, do you really think that, given today's legalistic environment, that information would ever see print?


"Maybe you need to be reminded of P.T. Barnums favorite quote. remember that one?"

You mean this one? "There's a sucker born every minute."

Would that be the sucker who's suckered into believing that the more/most expensive is ALWAYS the best choice for every application?