Pressures, .50 caliber rifles, strength of materials, PART 1
 

I earlier said that alot of powerful, effective deer killing loads could be operated under 10,000 psi. As a starting point, I would like to explain why and how that is possible, because for many, it may seem to be very anemic pressure for a hunting rifle. Lets consider a centerfire rifle first, say a 25-06. Loads for the 25-06 need to operate at peak pressures less than 51,000 psi and for 100 grain bullet, the muzzle energy is in the neighborhood of 2300 ft.lbs. Now the pressure impresses force on the bullet by the following equation

Force = Pressure (lb/sq in.) * Area of bore (sq. in.)

So at peak pressure, the force is:

Force = 51000 * (PI*.25^2)/4 = 2503 lbs. force

Now lets calculate the pressure required to generate the same force in .50 caliber. The big difference in pressure will come about by the dramatic increase in cross sectional bore area. Since area increases by the square of the bore diameter, doubling the bore size actually quadruples the cross sectional bore area. So lets calculate the pressure required to impress 2503 lbs force on a .50 cal projectile.

Pressure (psi)= Force (lbs force) / bore area (sq in.)

Pressure = 2503 / ((PI*.5^2)/4)= 12,750 psi

Are you surpised? Now think about a few things. The 25-06 isn't particularly efficient at delivering muzzle energy. With a 3200 fps MV, there is alot of friction in the bore. Also its going so fast that the time in which the breech gases have to accelerate the bullet is considerably shorter than in your muzzleloader. So you should see by now. That very, very, effective devastating deer, elk, and grizzly hunting loads can be loaded into your muzzleloader for a fraction of the risk, (and monetary cost), of a three pellet "magnum" load.

In my next, post i will discuss the strength of materials and how pressure translate into stresses within your barrels.

Happy Hunting, Phil

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

Taking the concept one step further would be a cannon. I built one of these when I was in high school. Used a 4" steel bar that was about 24" long. Bored a 2" hole in it. No rifling. Made a mold for casting a 1.9" lead ball. I would expect the pressures, even with a 1/4 can of black powder, were quite low.

However, the trend toward smaller bullets at higher velocities and pressures in undeniable. Mainly for long range trajectory and, to a lesser, degree, recoil I'm personally thinking about hunting with a 200 grain Shockwave in 2006. This .40 caliber bullet has a high BC and is going over 2300 comfortably; and could represent an honest 250 yard load. I like the big lead conicals but they start dropping off pretty fast beyond 150 yards.

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

Right, and I understand the need for the load you use. I also live in Colorado and if I used my ML in regular rifle Elk season, I would probably use a load just like the one you are using. I expect to draw antlered elk for statewide ML season this year and hope to call my elk close enough for a big lead conical.

Allow me to say this. I am not worried about you, sabotloader, and others who are very experienced with MLers. This is really for the benefit of individuals who have been frightened from using their Spanish barrelled rifles and people who have children who are not experienced with MLers.I am hoping to givethem an understanding which will give them some level of confidence that the Muzzleloader they purchase can be enjoyed and hunted with safely.

Happy Hunting, Phil

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

Pglasgow

I for one am interested in the development of this thread, in fact if I didn't have such a fond feeling for my Firebolt - I would offer it for any tests that you or Roskoe, as a gunsmith, might want to conduct with it. Actually they are so darn cheap we ought to take up a collection buy one for one of you guys- let you get behind a dirt wall and see what the thing will take. But I do not know what that would prove, because we are probably not qualified to make such a test. Well, I do not have the qualifications for it to mean anything other than myself....

looking forward to more information....

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

First let me say I am not an engineer, nor am I
a metel fatique specialist. I do however understand
FORCE/MASS/PRESSURE. I also own a 45cal with
the dreaded barrell. So keep me posted, I'm
never too old to learn. I do understand that
their are some who need close scrunity when
handling any ML. Most of these folks have no
idea of what really happens when they load
prime & touch off their ML. Just my 2-cents
Danny

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

With the top formula are you assuming a 100 gr bullet weight? If that's so since you used the 2503 then you have a 50 cal shooting a 100 gr bullet for that pressure. As you increase bullet weight the pressures go up. You'd be better off comparing something with a reasonable bullet weight. The minimum I'd use would be 240 gr. Your pressures will be higher than you think. Of course this doesn't take into account the differences between plastic (saboted bullets) and a copper jacketed lead bullet or bore conditions. The smoother the barrel the more velocity your pressure will give you. And plastic saboted bullets don't generate the friction of a copper jacketedbullet which would translate to slightly lower back pressure/increased velocity for the same bore. If your comparing the Copper jacketed bullet to a lead conical that doesn't equate right either. The lead will use some of the pressure to swell into the rifling. This is why comparing saboted bullets of equal weight the lead bullet will be somewhat slower. 100-200 FPS depending on bullet weight.

In reality formulas really don't tell you anything but theoreticals. The only way to know for sure is to use a test barrel specifically designed to test pressure. Strain gauges won't even give you accurate data. You can use them as a comparison tool but their use in muzzleloaders is shaky at best.

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

Wolfhound76

Patrick, I have read this term a couple of times now "strain gauge" I think I have the concept but I can not picture the physical apparatus and how it might be hooked up... Could you explain further to me?... and this is an honest question...

thanks mike

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

I guess I will be following this thread with interest too, it is one thing to understand what is going on in a rifle when you fire it, and quite another to be willing to take the time necessary to put it all into terms that some one with out the education or 40 or 50 years experience can understand.
I say good for you. Lee

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

Hey Danny,

It is important to know that with 45 cal., your pressures are going to be higher for an equal charge of powder and equal weight of projectile than in a .50 cal. Roughly, not exactly mind you, 66% higher. There are good reasons for this. Because the bore area is smaller, the pressure must rise above .50 cal pressure in order to accelerate a bullet at the same rate of accelleration as it does in 50 cal. In a .50 cal, because of the greater bore area, the breach volume expands faster than it does in .45cal, meaning that, pressures will build longer and won't drop as fast from the peak as they do in a 50 cal. That said .45 cal, because of the smaller bore, for the same pressure, will stress the barrel less, given the same wall thickness. I'll get into this in more detail in my next thread, its just a fancy way of saying that a .45 barrel with the same or thicker wall thickness can carry more pressure in the bore while stressing the barrel less than .50 cal.

There will be alot more on this subject Danny.

Happy Hunting, Phil

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

This is my understanding so if sombody noticesI'm wrong on something speak up.;)

A strain gauge is nothing more than electrodes placed on the barrel that are connected to a computer. They measure the flex of the metal. The problem is that you have to know exactly what alloy your barrel is and you have to place them in a certain place (over the bullet I believe). With muzzleloaders having no case a powder increase/decrease changes the place they have to be and and if they're not placed exactly right can give you false readings. Also I believe you have to calibrate them with a known load. It's just software and the electrode aparatus.

There's also another way to estimate pressure that relies on software and a chronograph. You imput the velocity, bullet etc. and it spits out a pressure graph. It's not that accurate either and can be off by a few thousandPSI if all the variables aren't right.Plus I don't think there's a version for muzzleloaders with all the extra variables we deal with so there's an error factor built in.

The only way to know for sure is a test barrel. And even that will be off because of variances in the bores. It's still by far the best way to do it.

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

Wolfhound76

I got the real pressure barrel concept, but I really was lacking information with the strain gauge apparatus. The concept I had - the how I didn't - the computer/electrode I do follow and I can follow the different allow thought.

But it something that I will not have or be able to use.

I am wondering... is there an independent engineer - naw that wouldn't be practicle either. There are just so many varibles in an ML..

Thanks for the info...

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

Re-read it Wolfhound. Take some time and it will all be clear to you. I don't have a 100 grain bullet in the .50 cal. The force on the bullet is completely independent of the bullet weight. All we calculated was how much pressure it takes to impress a given force onANY bullet. For a given force, it takes 4 times the pressure in .250 cal as it does in .500 cal. It is indisputable.

It is also indisputable that loads with peak pressures in the neibhorhood of 13000 psi can produce muzzle energies of 2300 ft. lbs. In .500 cal. that is.

Now that said. Given a particular charge. Will a heavier bullet cause higher pressures to build in the breech? You bet it will. But thats not the topic. The actual topic is this. One doesn't need 3 pyrodex pellets for a service load.

Happy Hunting, Phil

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

This is pretty close. The strain gauge is a electro-conductive sheet whose conductivity is a function of strain within itself. The sheet is attached to thebarrel with adhesive, and when the gun is fired, pressures expand the barrel stretching the electro-conductive sheet. If one can calibrate just how much the barrel was strained at a given point in time then it is possible to calculate pressure within the barrel at that location and time by knowing the dimensional properties of the barrel and the physical properties of steel of which the barrel is composed.

A strain gage does not take a direct measurement of pressure. Furthermore, it is unreliable as a measurement tool for pressure. The usefulness of a strain gage is more in "relational" data. That said. If it is calibrated with actual direct pressure measurement on the barrel on which they are installed, they can produce reliable data for the calculation of pressure.

Wolfhound76, if Randy is screwing around with strain guages, then don't trust any thing he tells you about them or the pressures he claims he is measuring. He's a friend of yours and I appreciate that, but I am correct in saying what I am saying, it simply will not hold in court against BPI'sdirect measurementpressure testing.

By the way, if you want to contribute beneficially to this thread, you could help me get data on the grades of steel used in the Spanish barrels, also Knights, NEF's, GM's, Whites, and T/C's. I can only assume Randy has this data. Will help us get this data? I need minimum yield strength and minimum tensile strength for the steels each uses.

Happy Hunting, Phil

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

"it simply will not hold in court against BPI'sdirect measurementpressure testing." Phil, whut testing?

Also think you should call RW directly if you would like him to provide information. I think you'll be in for a shock (hard to say what kind though ;)).

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

U.C.

I can not see BPI going to court without their own battery of tests, performed under stringent laboratory conditions, with direct measurement of pressure. Not strain gauge crap. Randy should be prepared for it. This notion that BPI is flying by the seat of its pants without any investment into the safety of their rifles, has GOT to be, false. Therefusalof BPI to provide Randy their due diligence is not "proof" that they didn't do their due diligence. Really, if I were any company, I would notgive anything to someone working for a law firm.

All I want is data. Real honest data. I'm asking you for it Randy. Give it to me please. All of the real honest properties of the materials. When you are done with that, please, just make a copy of everything, I mean everything. Every singletest you have ever done. How it was performed. How much charge, how far off the charge you are "short seating",how you "crack" pellets,so on and so forth. Precise accurate descriptions of the abuses the BPI and any other rifles are being put through in your home laboratory.

Now UC, I have formally asked Randy for it. I will be surprised if Randy supplies it. I don't know if Randy can supply it for the same reasons BPI didn't supply Randy with their data and testing. He can at the very least, supply the strengths of the steels.And if he does, I would appreciate it.

Some of things that T7 saiddidn't make all that much sense. Things like "soft extruded" and "bulge faster". It may well be that American barrels are "softer" at least in that they are more pliable capable of expanding without bursting when an abuse is done. Anyway, it is clear to me that this language is originating from Randy. As someone who is "GETTING PAID NOTHING", I would like to get as close to the bottom of this as I possibly can. Youcan help also, U. C., encourage Randy to supply it.

Something else is bothering me. I would also like Randy to explain what he found in his testing to encourage his continued support of Austin Halleck. You know, what he may think "is different" about the barrels.

Again, I understand he is a friend of yours, I do respect that.

Happy Hunting, Phil

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

No. I think your generalizing this too much. Pressure increases with bullet weight. The same powder charge will produce higher pressures with a heavier bullet than a lighter one while giving you less velocity. The way your saying this is that 12,750 psi and it doesn't matter what bullet. It does matter. You used aspecific bullet weight to generate the 51000 PSI in the 25 cal.For the formula to workyou have to use the same bullet weight in the 50 cal. It's not in the formula but if you change the parameters of how you got the PSI number you change the result. The numbers don't change, but the value to someone is suspect.

What would the pressure be in the 25 cal with a 75 gr bullet? With a 120 gr bullet? You change the bullet weight in the 25 cal you change the pressure. The pressure changes so does the result of the formula.But for the result to translate over to the 50 you have to use the same bullet weight.

If I remember right you used the max pressure of the 25 cal though.

So what is the pressure for the 100 gr bullet?


This is all theoretical and it's all nice and neat but it has no real world value.


And to answer the question about the strain gauge, no Randy does not use one. He uses the software/chrono version. And no I don't think he gets good data but he'll even admit the values can be off.

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

Good luck. He doesn't have a lab. The data he's got came from the companies themselves.

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

Thanks for your comments here, Wolfhound. Could you explain further? Take your time, and go into considerable detail. I was under the impression, from things that T7 wrote, that Randyhas determined through rigorous testing, that BPI rifles are not capable of taking the pressures american made rifles are capable of without bursting, while on the other hand, American made rifles merely bulge.

From what you said, it seems that Randy hasn't done any testing? He is not able to say that one barrel is softer than another or stronger than another, so on and so forth? Are the company's themselves providing Randy with data for the BPI barrels? I am confused how Randy is justified in drawing the conclusions he has.

Right now, I have the impression that Randy is more of a PR spokesman for the Law Firm as opposed to a "technical expert". And I fear, your friendship has been abused, in that, it seems Randy and the Law Firm use you, along with other well-meaning, sincere, and honest people;in this apparent "PR campaign".

Happy Hunting, Phil

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

Wolfhound,

You are quite confused. The problem you are having is that you fear where this thread is taking us. Let me tell you where we are going to go with it. I'll give you the "agenda" up front.

We are going to discover that people who encourage others to put 150 grains of pellets in their muzzleloaders, are givingadvice whichcan put the advised party in jeopardy. We are going to discover that giving people the impression that their muzzleloaderis without value or worth for hunting unless they load their MLer to 30,000 psiis misleading at best, a blatant outright lie at the worst.

It wasn't you who said that a Spanish barrel is proofed to only a third of a service load, was it? I don't remember. But if it was, then I forgive you because you couldn't have said that disingenuously, I think to highly of you to say that.

But thats where I am going with all this. I do hope that you approve of that. And for the life of me, I can't figure out why you wouldn't. Anyone who may change their loading practices as a result of this series can not help but to be safer, with a greater margin for mistakes, than what they were previously. You do support me in that, don't you?

Regarding the following:

You didn't specify the charge Wolfhound. You do know that there is no such thing as .50 cal 100 gr. bullet? But a very hollow one could feasibly be made. With 100 grains 2f BP, it would not be possible to exceed 4500 psi with say a ballet style 100 gr bullet. And of course, there is no way the muzzle energy is going to be 2300 ft.lbs.

To get the pressure up to 12750, we are going to have to choose a much heavier bullet, and if we do, we will have a very powerful, very effective, deer slayer in our hands.

This is what doesn't have any real world value.

"Soft extrudedbarrels bulge faster"

"The proofing is 1/3 of a service load"

"With max charges and monster bullets"

Just a few quips from acouple of well meaning and very naive guys who obviously don't are qualified to discuss such things.

Happy Hunting, Phil

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

Do you know what an extruded barrel is? They push the barrelthrough a die and at one end is a blank and the other is a barrel. The metal has to be very soft to do this. Currently the only barrels (other than the spanish muzzleloaders) that they use this process is paintball guns. Here is a very good post on the subject. Amost all the way down and posted by 1shot1kill.

http://www.huntamerica.com/wwwthreads/showflat.php?Cat=0&Number=386313&page=7&am p;fpart=18&vc=1

[/quote]Right now, I have the impression that Randy is more of a PR spokesman for the Law Firm as opposed to a "technical expert". And I fear, your friendship has been abused, in that, it seems Randy and the Law Firm use you, along with other well-meaning, sincere, and honest people;in this apparent "PR campaign".[/quote]

There is no PR campaign. This issue is over 2 years old. Well before Randy was contacted by the law firm in question. He started this THEN was contacted by the law firm about a couple cases. Read the date on the first post of the first page. This is nothing new. It started with questions about the proof. Here's a good post on the same page a little further up by RW.

If that's the case then the formulas you posted have no value. Everything has to be equal (exept one variable-bore diameter)for a result with a meaning. We were speaking hypothetically. A hypothetical bullet of 100 gr for 50 cal that fits the same in the bore as the 100 gr bullet in the 25 cal.and using the same powder charge and powderas the 51000 PSI 25 cal load. Anything else slants the results. If you want real information for real loads, check out "The CompleteBlackpowder Handbook". There are pressures listed. I don't have a copy but if you ask Randy maybe he'll give you some of the pressures.

By the way, I'm not into the magnumitus either. My favorite load is a 260 gr bullet with 100 gr FFG 777 loose at 1985 fps. 2275 ft/lbs at the muzzle. I have played with 3 pellet loads but I can count the number of such shots on one hand. I don't like the recoil.

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

Hey Wolfhound,

I've just been to your website. Listen, I like you. I think of all the people who have discussed this with me recently, you have been the most sincere about about giving clean, concise, information about what you know and think about it all. I respect that.

I just wanted to suggest, that maybe, it would be to your benefit, to be careful of the claims you make about things like strength of this rifle over that. It's your site, and you are totally responsible for its content. You have, I am sure, lots of valuable information to share which doesn't get into such things. Unlike Randy, I don't see where you have anything to gain, and in my opinion, much to lose.

I've always heard that advice is worth what you pay for it. So you may not value my advice at all. But to be honest, I think I am being a far better friend to you in saying this, than Randy is in encouraging you to further his causes and interests.

Happy Hunting, Phil

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

You see that is where you are wrong. Everything doesn't have to be equal, simply because, the bore diameters are not the same. Allow me to explain. What I chose to "make equal" was the force on the bullet. Nothing else. Just the force. And as I said, the force is only dependent on the pressure and the area of the bore. Has nothing to do with bullet weight. Nothing at all.

Now, why did I chose to makeforce equal? The answer is, because it is the forces which will determine whether the load isof sufficient energy and momentum to get the job done when hunting. We have two ways we can calculate the potential of a pressure curve to energize a projectile that it is propelling.

We can timeintegrate the Forceand calculate a summation of the impulse of the charge. If we divide that value by the weight of the projectile (in proper units of course) we will get the potential for muzzle velocity. It, of course, won't be the actualmuzzle velocity because there is friction in the bore, but we can determine precisely the Impulse, the muzzle velocity, and the impulse absorbed by friction to great precision. Which also means that we can determine the efficiency of the charge's impulse on the bullet to great precision.

Further we can calculate the potential for Muzzle Energy by displacement integrating the Force.

In both cases, it the integration of Force which is required to calculate energies and momentum. So it should be clear, I chose the appropriate thing to be equal. The force.

Happy Hunting, Phil

RE: Pressures, .50 caliber rifles, strength of materials, PART 1
 

So does one assume just because a company did not test at a pressure level of other manufactures that the rifle is not safe by the guidelines set forth by the same mfg? An assumtion to fact are two different things. I feel confident shooting my BPI weapons within the specs that came with the guns.

As far as the barrels being extruded many are in both bp and cartridge guns. I guess we can call all centerfire barrels made this way unsafe also?

Just wondering I am not getting into the thick of this because I hardly run any charge near maxi.