The Mystery Of PRESSURE

I very much enjoy real HandLoading. In many ways I look at it as a Science. Now I am not talking about sitting down and loading 500-1000 45 ACP or other bulk loading….. that is Reloading, not HandLoading……… And yes, I do that too, and a Lot of it…. Sometimes after doing the Science it turns into a Loading job too………

No matter whether it is HandLoading Rifle or handgun, or just bulk loading, you whether you realize it or not, are dealing with PRESSURES. I seriously doubt that anyone that reads this has an Oehler Unit laying around that you take your ammo and test it before loading. You would have to be pretty damn serious about your ammo if you did. Still, you are relying on information gathered from somewhere, either your own test work, that can be done without such equipment, and or other sources such as a simple "reloading" or hand loading manual.

Pressure can be a total Mystery to us if we don't understand a little more about it and how some things work.
It took many years of doing pressures before I learned, there really is no help out there, what you will learn is from the books, manuals, and sources that may not be as reliable as you would like. Much of it you will have to learn on your own.

I started working with pressures back in 2003 I believe using a little known unit called Pressure Trace 1 from RSI. Using strain gages on regular rifles. Back in those days it was my belief that using a regular normal rifle for such things was actually better than having a special Pressure Trace gun done, with special barrels. Today I realize that I was correct in that, at least for our purposes. Regular rifles are not built to the same "TIGHT" specs a test barrel is. No two barrels are the same, you see that every day on the range, one shoot better, one faster, and what have you. Same with pressures. Perhaps if you were Hornady, or one of the larger manufacturers of bullets and components, a pressure gun makes sense, easy change out of barrels and so forth, but pressure barrels will only give you a start point, you are not using a pressure barrel out in the field, you are using real rifles and handguns.

Strain gages are extremely sensitive, they pick up everything, and you have to go through a really big learning curve to understand what you are actually seeing. I have a good example of this. The fellow that owns RSI is Jim Ristow. It was a major pain in the ass going through the learning curve, with very little help. Ristow really did not know as much as he thought he knew about pressures and his own unit. In the beginning I was running several rifles, 358 STA, 458 Lott, 458 Winchester, and several others in the early years. On many rifles I would get a incredible secondary peak, Primary or first peak would be normal, anything from say 60000 PSI or so, Secondary would go to 100000 PSI or more???? What in the world? Crazy. I did not know, did not like it, so one day I spent about 6 hours on the phone with Ristow about this. He went on and on about this or that, today I know now, he did not know anymore than I did about it.

Of course there was no such thing as having a secondary peak out there at 100000 PSI or more, in the end it was just electrical is all. The 358 STA was the worst at giving a large secondary, I decided to change the gage and redo it, and low and behold, the peak went away! Today, anytime I start getting that secondary peak, larger than primary, its nothing but a wire, or a gage or something such as that, nothing more.

Now, with that being said, sometimes there are actual secondary peaks, small ones that bump up as the bullet exits. This occurs with CERTAIN BULLETS most of the time. For instance, Hornady DGS and Swift A Frames have small secondary bumps at the end of the curve in most calibers. While other bullets in the same caliber do not. Strain gages are very very sensitive, and if you have the right software that you can see the curve and what it does, then you can learn a hell of a lot.

Here below you will see my friend Sam Rose, he is at the bench with a double rifle hooked up to a PT 1 Unit





I really had no idea in those early years just how damn good Pressure Trace 1 is, or WAS I might say. There is no more Pressure Trace 1 units available. Ristow is a decent software fellow, but hardware he is not. Some older fellow actually built Pressure Trace 1. Then he DIED! And everything about Pressure Trace 1 he took to the grave with him! Ristow had NOTHING after that, with the exception of spare parts and what few units were on the shelves! THE END. I had fired literally 1000s upon top of 1000s of rounds through Pressure Trace 1, and had sent it back several times to have small connection parts replaced, as they would loosen up, and start causing issues with reading the pressures, loose wires, connections, and so forth.

I did all the B&M work with PT 1. Starting from ZERO basically. There was nothing to go by, no known powders, pressures, and I also had to learn exactly how RUM and WSM brass worked to even study the brass. Using PT 1, and comparing brass measurements, and by listening to what the rifle said to you, how it reacted with bolt lift, I really started to believe more strongly in PT 1 and what it was telling me. Between PT 1, and the other indicators, I found everything was matching up very very close.

By the last time I sent PT 1 in for repairs, I was told I had the very last of the spare parts, there were no more to be had, none that could be made, that was it. By then I had finally learned that PT 1 was absolutely a Stand Alone System, in other words, it was so good that the readings you got from it were real, and no calibration or anything required, if you had good gages, wires, and good connections! Today, I know that PT 1 for $500 back in the day, is every damn bit as good as my $10’000.00 Oehler Unit! Had someone been smart, PT 1 would OWN that market today! In fact, when it comes to software, and the reports, the RSI Software is Far Far Far superior to the Oehler much OUTDATED software. You can learn more from the PT units than the Oehler Software can show you looking at the curves! Here are examples of the reports I see……….. Judge which one is better for yourself!

Oehler System 83 Reports...............







Nothing really wrong here, you get the correct Pressures, you get a Stand Alone System, what you see is what you got!… But, when compared to the PT Software, to me, this really comes up short……………

I have run the PT Software so much, one can really see what is going on with the Curve, and how things work, burn, and what is happening in there! Here is a very nice test with 416 B&M……….. These are the kind of tests I really love to see…………







You can see there is a hell of a lot of difference between the two Software systems. To me, the Oehler is for SHIT! Other than stand alone and give you something to work with……….

With the last of the spare parts used up for PT 1, I was beginning to get concerned about being able to continue to work with pressures. If something happened to PT 1, I was screwed, along with all the data I had collected. I decided to get a new Pressure Trace 2 unit and see how that worked.

Pressure Trace 2 was built AFTER PT 1 was no longer a viable product. It did away with the wired connection to the computer, and uses Bluetooth to exchange the data from the strain gage, to the computer…….. I never liked bluetooth anything, but there was the PT 2, or the Oehler, and I was not ready at that time to commit to the Oehler! PT 2 cost a bit over $500, not a big investment. So, I got one on the way, but then it would not connect, no matter what I did I could not get the damned thing to work. Back to RSI! They checked it, said it was fine, sent it back, again it would not work, or connect…… This went on for weeks, email and phone back and forth. Finally I had enough of this BS, told Jim I was sending the unit back, they buy a laptop for me, set the damned thing up, get it to working, then send it back. Now this is after sending the unit back a time or two, along with my laptop I already had for PT 1, this was the last straw! It had finally gone 7-8 months of aggravation. At one point I told Jim I would just as soon put the unit downrange and blow it all to hell as to mess with it anymore! And I meant every damn word of it, and it came close…………

Finally, got the unit back, with its dedicated laptop, THEY SET IT UP, and it actually worked! Oh, by working I mean I could get a trace, but it was NOT CORRECT. I had known pressures, in particular in the 50 B&M Alaskan Marlin I had been using. This gun talked really good, it locked up at 46000-47000 PSI, so I knew what max loads were in this gun. A 44000 PSI load showed about 25000 PSI on the PT 2, so I knew this was bull shit from the beginning. According to RSI however, the PT 2 was RIGHT……. There were some serious debates and arguments over this, some which ended again in blowing this POS all to hell and calling Oehler!……. HEH HEH…. What a mess……… OK, fine, no need to argue, I actually know more about this than they do, so I just dropped it and I figured out how to calibrate PT 2 with PT 1. When I figured out how to do that, then PT 2 worked great from that point. PT 2 IS NOT A STAND ALONE UNIT, it has to be calibrated to a known pressure. Once I had a rifle/cartridge calibrated, then PT 2 was a viable unit.

Now, all I had to calibrate PT 2 was with Prior tests done with PT 1, OR use PT 1 for the Unknown, and then Calibrate PT 2 from that point. What the hell would I do if PT 1 went down for the final time? On any new work, any new rifle or cartridge, I would have no way in hell to calibrate PT 2, so it would be lost as well….. and useless…………..

Time to bite the big bullet if I wanted to continue any sort of research, and I do love doing these sort of things, and having that capability, so I started talking to Oehler!!!!!!!

Oehler, the industry standard…… I got a good dose of “STICKER SHOCK” you might say….. The first quote I got, System 83, with chronograph, no ballistic downrange targets and all that mess, don’t need that…. was around $12’500.00 OUCH…….. I had not requested the chronograph, so we negotiated that OUT, and got the price down to a bit more than $10’000.00, so I ordered one. Now I got some more surprises too, disappointed surprises at that. Now here is a $10’000 unit, and I was going to have to make up my own strain gages? I was also going to have to make my own wire hookups? They did not even have strain gages available, I was going to have to outsource them! Unit uses a standard telephone wire and connector, so that was not going to be a big deal, but me doing the soldering and such to those tiny strain gages? No way!

Talking to the Oehler people we decided the READY MADE strain gages from RSI were the SAME exact gages they used anyway, and with those hookups the Oehler would work fine. Whew, thanks to RSI (pissed me off a little) I could use the same gages, ready made, nice connectors already made up at around $25 each! I still had to solder and connect the RSI connectors to a telephone wire, but that I could handle. And did.

They had to build my System 83, the newest and greatest from Oehler. It arrived, and actually looks like something made in the 1980s in its aluminum box! LOL…………… Much talking to Oehler, they assured me that it was a “Stand Alone System”, required no calibrations, and it would be “What you See is What You Get”………….. When it arrived, I could not wait to test it, so I had known, OR WHAT I THOUGHT WAS KNOWN, loads ready to go in several rifles and cartridges. I input all the required data, which was actually some less than what was required on the RSI systems……. and started shooting…………. I admit, I was concerned what would happen, what would I do, if the Oehler system did not match all the work I had done for 10++ years?

Within an Hour, I WAS a happy boy ………….. Every reading the Oehler took, matched damn near perfect with everything I had expected and hoped for!!!!!! I WAS EXTREMELY pleased with this, all my work for years matched the industry standard equipment!

This really did show me just how damn good PT 1 was!

The box the Oehler is built around matches the software they still use, 20-25 years outdated as I figure it! Those little nothing pressure trace curves on the Oehler, you can’t learn much from those. The RSI software was light years ahead, in my opinion anyway. But, it does make the Oehler easy to work with, and very few issues……….









The box the Oehler is built around matches the software they still use, 20-25 years outdated as I figure it! Those little nothing pressure trace curves on the Oehler, you can’t learn much from those. The RSI software was light years ahead, in my opinion anyway. But, it does make the Oehler easy to work with, and very few issues……….

None the less I finally had all my systems here worked out. I now use the Oehler to obtain stand alone data and calibrate PT 2 from the Oehler. Once that is done, PT 2 runs great, especially when I want to look at how things are burning and what the curve is doing. You will be amazed at what can be learned just by studying the curve and how it reacts……. I really enjoy running pressures, lots of work, but very rewarding in the end…… Regardless of how you do pressures, its all still just an estimate, in this case I feel like its a very close estimate, but not an absolute.

Fortunately in the B&M rifles they are all done with the same barrels, same reamers, same builders–SSK Industries. While not a clone copy in every case, they are very close from what I have seen. Other rifles, different chamber specs, different barrels and so on, best you can hope for is that the data is in the ballpark, maybe close in some cases, but one should always move smart and safe by starting under any published data, mine or anyone else’s………

Wow good stuff. Not sure how this is going to help me buy a new car but excellent write up! I did think I was special cause I reloaded; now I'm pretty crushed about that.

Pressures are very important to the hand loader. And somewhat of a mystery to most of us. There are so many variables involved, that there are very very few absolutes……

Ken Oehler says this at the very beginning of the System 83 Manual.

Chamber pressure measurement is a blend of science, black art, and common sense. There are few absolutes; the best we can expect is to reliably distinguish between the safe and the unsafe. Pressure measurements are tedious, but they must be made. Pressures will literally rise up to smite the unwary.

You Must Understand This………. And take it to heart, when considering Pressures…. All Pressures, From ANY SOURCE………

You may read that the pressure of a certain load is 56,000 psi. You must not assume that the 56,000 psi is an absolute number. The 56,000 psi number by itself does not tell you the pressure that will be generated when you fire the ammo in any specific test barrel or gun. The pressure generated by the round depends greatly on the gun in which it is fired and the test conditions. Individual chamber and barrel tolerances are critical. The pressure numbers so casually mentioned with great authority are not absolute; they are approximate and they are only relative!

The pressures measured in any specific gun with the either piezo transducer or strain gage apply only to that gun. You can use the pressure numbers to compare different ammo fired in the same gun with the same instrumentation. Strain gage readings from the M83 correspond closely to pressures in hundreds of pounds per square inch. Pressures in sporting gun will typically be lower than pressures of the same ammo fired in a standard test barrel because the test barrel is intentionally made tighter than typical sporting barrels. Just as some barrels shoot accurately and some won’t, the same ammo builds different pressures in different barrels.

During my years of running pressures it is very true, there are very few ABSOLUTES you can count on. But, there are some BASIC RULES you can count on.

#1.....Weight Always Equals Pressure! The heavy bullet will always take more pressure to move than a lighter one. Use the same load, heavy will give more pressure.

#2....Bearing surface equals pressure! The more bearing surface a bullet has, all else equal, the more pressure it will produce.

#3....Diameter equals pressure, all else being equal in the same caliber, a .001 more difference will give more pressure

I test pressures at my 25 yard bench on the indoor range. Tables and computers are set up next to the bench, and of course, The Round Table that we sit around and discuss bull shit after the test session HEH....





Now that you know the basic setup here, we can discuss how you at home can look at pressures and how to work with it without all this equipment......................

Remember this, there are no free rides, well, ALMOST anyway. Some point later, I will tell you about a "Free Ride" experience, but it was out of normal circumstances........

Basic rule is, if you are getting faster velocity with a given load, that is out of norm, then you are also getting HIGHER PRESSURES. I see this a lot when you have a particular load, with a particular powder. Then you buy a new can, or keg of that same powder, many times within the same lot# as well, and all the sudden you get more velocity than the old keg or can of powder you used before! Well friend, I am here to tell you, that 99% of the time you have not found a Magic Keg of powder. You are getting more velocity because you are running higher pressures. Use percentages. If you are at the top end of Maximum Pressure, what percentage more velocity are you getting than before? Chances are you are running that same percentage more in Pressure as well. If at Max pressure before, you are now OVER MAX PRESSURE, and you best drop the load back down to your previous velocity to equal your previous pressures.........

Your brass may be talking to you as well. Watching primers is an indicator, but nothing more. Some primers may be softer than others, even the same make and model! So primer flow may not be the best indicator, but to be combined with more accurate methods such as case head expansion measurements. It's tedious and time consuming, but if you have some basic measurements to back up on, you write those down and keep them. Use the same
brass of course, Hornady brass may expand more than Norma brass, and so forth....... If you know the how much the case head expanded with the old load, same brass, then you can measure your new load at the same point and get an idea from that.

Your rifle will also talk to you, if you listen properly. An example is heavier bolt lift in bolt guns. When you start to experience that, you are already in most cases getting over Max Pressures. Most of you already know this.

At times I would get too lazy to run pressures, hook up gages, and do the data. I would always measure case head expansion, and kept records of it. This along with other indicators will help you measure your loads more accurately.

@Toprudder, so here is @Michael458 with this great long post and all he has really done is present us with a bottle labeled "DRINK ME"! Now I know what happened to Alice, but damn if I am not thinking about it.

Imagine the pressure studies comparing non-concentric rounds against concentric; The impact of neck tension on pressure, or even now with the New AutoTrickler V3 and an A&D balance, the impact of a single kernel of powder on pressure!!!!

But then there is a great deal of expense involved, and I am not sure that I could answer the three questions above in the time that I have left on earth, and my wife would certainly point that out at some point before threatening divorce. (She is nice like that) That said, it is a project that I could begin and my sons could finish. THAT'S IT! I can buy it for my sons! Problem with the wife solved, and the project now completely justified in mind.

Life sure was a lot more simple when I only played with shotguns, but damn, I'm getting good at this!!!

Thank @Michael458, fun to ponder, and I hope to see some articles on your data some day. Interesting story.

Have you tried sourcing another company to repair/upgrade PT-1?
Flight Systems has done some great work for us on obsolete cards, I don’t know if they would be helpful.

Pink_Vapor said:

Have you tried sourcing another company to repair/upgrade PT-1?

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Some years ago I considered something like this, but never really did it. I am sure some genius could recreate it. It is an incredible piece of work, considering the cost. It really is a shame that the technology is not available now. It is, was, a total stand alone, what you see is what you get tool. It was available to everyone, and at $500 a pop, not out of reach at all for most handloaders. Whereas PT 2 uses the same software, which is great, but it is not stand alone and has to be calibrated. Now how in the hell RSI figures that the everyday hand loader has a way to calibrate the system I don't know. They say use a industry standard, say you find a load that is doing 56000 PSI, then you calibrate the machine using that. But that is not your load, your powder, your rifle, brass, or other components. There are just way too many variables involved to do that.......... As stated, I use the PT 2 system, but only after I calibrate data from either the Oehler or PT 1. Same rifle, load, powder, bullet brass and so forth........ Then it is right from that point on.

I now have two PT 1 systems. Somewhere Sam found one that was still new in the box and bought it. He sent it here for us to keep put away. I am a bit lazy these days, and not currently involved in a project that requires a closer look a the curves and what they are doing. Mostly just hook up to the Oehler to get various data, such as when a powder change is made, or in the case of doing the load data recently on the 358 MGP. Hook ups are fast and easy.

Charlie R said:

Thank @Michael458, fun to ponder, and I hope to see some articles on your data some day. Interesting story.

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Charlie R....... There have been several articles and such on projects we did here, but I didn't write them, others have.......

Newboy said:

how are you calibrating a rifle to know you are getting correct pressure readings?

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OK, you don't calibrate the rifle itself. When I am talking about calibration, I am talking about the one unit, the Pressure Trace II Unit. Since it is not stand alone, get what you see, it has to be calibrated to some source that is as close to absolute as we can be. Remember, there are only a few absolutes involved. The Oehler System 83 and the Pressure Trace 1 Units are "Stand Alone", when you get readings, reports, and data, Pressures, from these units, its as as good as it gets, with that rifle, powder, case, and so forth. If you get a reading of 50000 PSI with the Oehler or PT 1, then you would then hook up PT II to that same rifle, use that same bullet, case, powder, primer and so forth to calibrate PT II to that pressure. Say PT II gave you a pressure of 40000 PSI with that same load. Then you would tweak the PT II to match 50000 PSI, and shoot again to make sure that you were in the ball park.

The Oehler and PT 1 will give you stand alone information in which to go by. Neither of these units require any calibration, other than to input how much pressure the case can hold, which is normally anything from 5000 to 10000 PSI. This has to be input in the beginning when you are setting up either the Oehler or PT 1 for a particular rifle. Strain gages measure how much the barrel expands at a point over center of the chamber. This is then calculated by the computer program into PSI.

As stated above, I believe the RSI Software to be far superior to the outdated Oehler software. At least any versions that I have. What I like most about the RSI software is seeing more detail about the Pressure Curve and what it does with various loads.

As an example below, which one of these loads would you choose? Which one just by looking at the Pressure Curve?

You get really excited about your load when you see Pressure Curves like this along with the close numbers.................

Michael458 said:

Some years ago I considered something like this, but never really did it. I am sure some genius could recreate it. It is an incredible piece of work, considering the cost. It really is a shame that the technology is not available now. It is, was, a total stand alone, what you see is what you get tool. It was available to everyone, and at $500 a pop, not out of reach at all for most handloaders. Whereas PT 2 uses the same software, which is great, but it is not stand alone and has to be calibrated. Now how in the hell RSI figures that the everyday hand loader has a way to calibrate the system I don't know. They say use a industry standard, say you find a load that is doing 56000 PSI, then you calibrate the machine using that. But that is not your load, your powder, your rifle, brass, or other components. There are just way too many variables involved to do that.......... As stated, I use the PT 2 system, but only after I calibrate data from either the Oehler or PT 1. Same rifle, load, powder, bullet brass and so forth........ Then it is right from that point on.

I now have two PT 1 systems. Somewhere Sam found one that was still new in the box and bought it. He sent it here for us to keep put away. I am a bit lazy these days, and not currently involved in a project that requires a closer look a the curves and what they are doing. Mostly just hook up to the Oehler to get various data, such as when a powder change is made, or in the case of doing the load data recently on the 358 MGP. Hook ups are fast and easy.

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We were having $1,000 cards rebuilt for $150 and a 3 yr warranty.

Pink_Vapor said:

We were having $1,000 cards rebuilt for $150 and a 3 yr warranty.

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That is incredible. Hmmmm..... Thinking on that. Might want to get that contact info from you and see if they could reproduce this?

Below is a paste and copy version of a post I did a few years ago, pertaining to some of the things we are talking about on this thread concerning pressures and some of the things you need to look out for...............

Over the years many of you have heard me say “My Powder is NOT your Powder”, so beware! This means that regardless of where you get a load from, me, someone else, the various loading manuals, always beware that powder can change its burning characteristics, and not just from Lot to Lot, but from one can to the next, within the same lot#. Hell, I don’t even look at Lot#s anymore, waste of time, not to mention it can be dangerous!

Many times over the years I have found major differences in powders, from one can, or keg to the next. The Reloader powders are at the top of my list here for differences. RL 15 is notorious for this, I have had RL 10X that changed so much that it could have been extremely dangerous, and just yesterday I have a major difference in my RL 7 from a lot I mixed in 2013 and did data for, and a newer lot from 2015. I have seen some differences as well in the IMRs, and Hodgdon. So TRUST NO POWDER FROM ONE KEG TO THE NEXT!

For several years now I order powder in larger containers, when getting several containers, I mix them all together. For instance right now I have 15 lbs of RL 10X coming this week, or first of the week, I will take all 15 lbs and mix it together, then test it to make sure of where it stands with what I have currently. I also have 15 lbs of RL 7 coming too, same story, I will mix it all together, then test it to see where it comes in at………..

This week I got back on my 308 loading project. I changed from my 2013 mix to a new 2015 mix of RL 7. Damn I was too lazy to worry with it, so I started loading…….. I had 150 pieces of fired brass, once I got to the end of those, I had some military brass and figured I best might check the pressures before loading that. I needed a NEW baseline to start from, so I used some of the Federal new brass I had to get that new baseline of 42/RL 7–2015 blend!

Well low and behold the baseline jumped from the 2013 blend of 51000-52000 all the way to 58000-59000 with the 2015 Blend!!!!!!!!

The LC and other mil brass went to 60000+…………..

Now I also saw other indicators as well. The bolt gun did not like that 58000+, bolt little scratchy on open. Brass showed it and primers as well. But the big indicator was also the Velocity…. It was UP by average of 150-175 fps over the same load with the 2013 blend of RL 7!

You don’t have to have an Oehler System 83 to know that there is no free rides! Increased Velocity equals Increased Pressures, there is no magic involved, one thing leads to another and no way to avoid it. So even without a Oehler to measure pressures, if you see that sort of increase in velocity, then you know you are running far more pressure than you were running, SLOW IT DOWN, to match what you had in the past………..

This is exactly what I did, start reducing RL 7-2015 blend to MATCH the Pressures and Velocity to what the 2013-Blend gave me………

Long story SHORT……. I had to drop the 2015 RL 7 blend from 42 to 39.5 grains to match the 2013 blend of RL 7……….. Velocity matched up perfectly as well.

To go another step in this, I tried the 2015 at 42/RL 7 in the 16 inch DPMS. Normal 52000 PSI 2013 blend gives 2950 fps in this gun…… The 2015 Blend of 42 gave 3150 fps, and it hammered the brass, ugly shiny spots on the rear, ejection marks. Gun worked perfect, but was far over pressure for a semi. At 39.5/RL 7-2015 blend everything fell right back in place 2963 and 2953 fps and 51500 PSI.

Man I hate it, aggravating as hell to worry with, but if you don’t do it, you can run into serious issues and problems! Don’t be lazy, when busting open a new keg, check the velocities on it before loading a large batch of them!

All my RL 7 may change when I blend that new 15 lbs coming. I am going to mix the entire batch, including the 2015 I still have on hand, this is the only way I can ensure that I have a steady mix until that is gone, then start again……………

Michael

There are so many variables, that many of us don't consider when loading, that we need to take a close look at...........I ran across this example when Sam and I were testing and doing load data for 500 Nitro.

In this data the top loads you see are tests with the same powder, bullet, primers, but different manufacturers of Brass, Jamison, Hornady, Federal and Bell 500 NE Brass. Further down you see load comparisons of two different
kegs of powder, in this case, RL 15..........These are sizable differences. And if you were at top end Maximum loads, some of this would get you in trouble fast. For double rifles we set the max pressure at 45000 PSI.

I am also prone to doing some blending of different powders here, always in search of the "Magic Powder"........... Sometimes it works, sometimes it don't.............

Here is an example of not following the rules and understanding pressures and how they work.

Billy and I have a close friend, I won't mention names, but this is what happened..........

A couple of months ago I related a story about a friend of mine who made a very serious mistake extrapolating data from 30/06 to 6.5/06………..

Short story……..Only a month ago my good friend BLANK popped in with a real hang dog face. Hands full of manuals and paperwork. “What’s the problem BLANK?”………. I have forgot what exact cartridge he was trying to get a load for, and the bullet, but it was a smaller caliber, I believe .264 or .284, bullet weights same in both this cartridge of his, and a 30/06. Problem was, he wanted to try a certain powder that was listed on the 30/06 data, BUT NOT THE SMALLER CALIBER CARTRIDGE……… Now BLANK had some couple of issues going on here, smaller caliber being one of them, and POWDER being the other……. Not from Bullet to Bullet in the same caliber, cartridge and powder! Now this really gets difficult…….. He was dead set on this powder. OK, I looked at the data from the 30/06, found a few powders that listed on the 30/06 and the smaller caliber cartridge, compared them with the smaller caliber cartridge and found that most all were around 25% less powder with same weight bullet as the 30/06. So, I took the load from the 30/06, reduced it by 25%, and then Told BLANK to reduce that another 10% to be on the safe side. And started to go look for a burn chart, to see where this powder fell in at, and if it was close to the same burn rates that some other powders where that compared in both cartridges……..

He held up his hand, dropped his head, and said don’t go any further…….. Puzzled, I looked at him, and he said, “Already To Late”………
???????………… He had already BLOWN the gun! My man did not take into account, Lesser Caliber Equals more Pressure, he extrapolated Data STRAIGHT from a 100 gr 30/06 to a 100 gr bullet in a smaller caliber, did not reduce the charge at all………. Now you can take data from a smaller caliber and go the other way, checking burn rates first, and be safer. Larger Caliber, less pressures, equal weight, equal bearing surface, or close……… But not from Large to Small………………….. A costly error……… Maybe had he come to me first might have saved that gun……….

BLANK dropped by yesterday afternoon, he had sent the bolt and the case somewhere, and had just got it back, and wanted me to see it…… Holy Cow, I thought I had done a bad thing a few years ago when I blew a M70 6.5 WSM…. This was incredible…… It was a Remington, and a testament to just how strong a bolt gun can be. How it did not blow all to hell I do not know, take a look………

The primer pocket of the case, and next, the primer pocket with a Fed 210 Primer sitting in it for comparison………

A few years ago I was loading some test loads for a 6.5 WSM. Phone rang, got on the phone, but continued to LOAD (VERY BAD). The test load called for some sort of H powder, and I had H-4198 on the bench, and was not paying attention! I loaded a dose of H-4198, WAY too fast for this case, I forget, but was probably going to test H-4350 or something such as that. Locked it up TIGHT. After MUCH BEATING with a VERY BIG HAMMER, I removed the case. I thought I had really done some damage and a bad deed, but nothing compared to this 6.5/06…….My bad deed ruined a Winchester M70 Action by expanding it .003. I keep it and this case on the shelf as a reminder to pay attention to what you are doing when in the loading room.

Now what is even more amazing than the case and primer pocket, is the BOLT FACE itself!

Here you see both the bolt face and case head…. Take note of how the rim of the bolt face took on the same shape as the case!

And take note of how the case fits like a puzzle, back in the bolt face…….

Don’t do this at home guys………….. VERY BAD……

WOW!!!!

"WOW!" is right. Well, I guess the whole "3 rings of steel" spiel isn't just marketing judging from the pictures above. I wonder is there is any mathematical way to semi-accurately model the pressure of that round????

Thanks for the "Scared Straight Program" on interpolating powder data!!!!!

So @Michael458, given that you demonstrate enough knowledge and experience to instantly become our resident SME on all things related to chamber pressure (and thanks for the lesson) perhaps you can comment on a theory I have on the subject.

I would expect a somewhat linear relationship between powder charge and both velocity and chamber pressure but only up to the point where you start approaching maximum loads. At that point the velocity and chamber pressure would increase expotentially with only minor increases in powder charge. Would that be consistent with your experience or are you like me in that I don't really want to find out what happens beyond that point?

Charlie R said:

Well, I guess the whole "3 rings of steel" spiel isn't just marketing judging from the pictures above.

Click to expand...

I don't have anything to sell you, so not marketing anything..............

Charlie R said:

I wonder is there is any mathematical way to semi-accurately model the pressure of that round????

Click to expand...

Probably, but not by me....?? A hell of a lot..........

Michael458 said:

I don't have anything to sell you, so not marketing anything..............

Click to expand...

Sorry, I didn't mean you at all. A guy that used to work for me was VP Sales Remington Rifles for a while and that was one of Remington's big sales pitches for the 700, "The 3 rings of steel" making it safer. Your story and pictures would certainly support that claim anecdotally to say the least.

Howland said:

relationship between powder charge and both velocity and chamber pressure but only up to the point where you start approaching maximum loads.

Click to expand...

Rule of thumb only....... Most of the time when you reach or start to get close to Max Pressure for any given cartridge, velocity gains become less with the same amount of powder you have been going up. Easy terms, if you have been adding 2 grains of powder, and getting 50 fps gains, and you add 2 more and get only 20 fps, then as a rule of thumb you are close to top end.

And the big variable is the powder type you are using, and the cartridge. I have seen odd and strange things occur with different powders. Cartridges as well do not always react. There is a lot of interaction with inside case capacity differences, short columns of powder vs longer columns, air space, or compressed.... and the list can go on to cover even more........ These things are the Mystery part of the equation.

Also I have run a lot of tests at higher than normal pressures. If the gun holds, things really get squirrelly from 7500-85000 fps. The smallest change can drive one insane. I once helped with a proof load, they wanted the pressures at 75000 PSI, and planned to shoot 1 round in each gun before leaving the factory. Had a hell of a time getting a load. First thing was, ran out of bullets, bought same bullet but different lot#, and got stupid results. Ended up had to order 500 of the same lot# to get where we needed. It ended up being 4 very very long days, daylight until way past zero dark thirty each day...............

Charlie R said:

Sorry, I didn't mean you at all. A guy that used to work for me was VP Sales Remington Rifles for a while and that was one of Remington's big sales pitches for the 700, "The 3 rings of steel" making it safer. Your story and pictures would certainly support that claim anecdotally to say the least.

Click to expand...

Oppps, sorry, did not catch on, not much of a Remington fan here, however, can't bitch about the strength of that particular gun at all.........Thanks for the clarification..........

Howland said:

Would that be consistent with your experience or are you like me in that I don't really want to find out what happens beyond that point?

Click to expand...

Honest Howland, it would be hard to put consistent in the sentence when there are so many other variables involved. You could use the term consistent with one rifle, one cartridge, one bullet and one powder, but beyond that
things go to crap.........

Very few absolutes. Rules of Thumb are hard to pin down also.

Michael458 said:

Rule of thumb only....... Most of the time when you reach or start to get close to Max Pressure for any given cartridge, velocity gains become less with the same amount of powder you have been going up. Easy terms, if you have been adding 2 grains of powder, and getting 50 fps gains, and you add 2 more and get only 20 fps, then as a rule of thumb you are close to top end.

And the big variable is the powder type you are using, and the cartridge. I have seen odd and strange things occur with different powders. Cartridges as well do not always react. There is a lot of interaction with inside case capacity differences, short columns of powder vs longer columns, air space, or compressed.... and the list can go on to cover even more........ These things are the Mystery part of the equation.

Also I have run a lot of tests at higher than normal pressures. If the gun holds, things really get squirrelly from 7500-85000 fps. The smallest change can drive one insane. I once helped with a proof load, they wanted the pressures at 75000 PSI, and planned to shoot 1 round in each gun before leaving the factory. Had a hell of a time getting a load. First thing was, ran out of bullets, bought same bullet but different lot#, and got stupid results. Ended up had to order 500 of the same lot# to get where we needed. It ended up being 4 very very long days, daylight until way past zero dark thirty each day...............

Click to expand...

Powder:

Would you say the "mystery" as some call it can be found in a powders ability to be dense but not compressed? Example flake, ball, stick.

Keeping this "idea" in context of same caliber and such

JBoyette said:

Would you say the "mystery" as some call it can be found in a powders ability to be dense but not compressed? Example flake, ball, stick.

Click to expand...

No, once you understand how certain powders work, and in what capacities, it takes a lot of the mystery out of the equation. Some folks get concerned about compressed loads, and its a no go in some situations, however in
big bore rifles compressed can be a great advantage in many ways. Whether Flake, Ball or extruded makes little difference if you understand burn rates and how things work........

Michael458 said:

No, once you understand how certain powders work, and in what capacities, it takes a lot of the mystery out of the equation. Some folks get concerned about compressed loads, and its a no go in some situations, however in
big bore rifles compressed can be a great advantage in many ways. Whether Flake, Ball or extruded makes little difference if you understand burn rates and how things work........

Click to expand...

@Michael458 it sounds as if you may be able to shed some light on a thread on charge detonation on this same board.
Danger of powder charges that are small in relation to case volume?