I have a forest for the trees problem with the first thread on this subject, as the test will not answer what i feel is a more practical and useful question. My hypothesis is that:

In a given bolt action rifle, using a fixed set of reloading components, chronographed velocity is a very good indicator of chamber pressure.

Now, I work for a very large defense contractor that has done extensive internal ballistics research for the Dept of Defense, and we have a lot of small arms data suggesting that this is a correct hypothesis. In fact, the coefficient of correlation for average peak chamber pressure and velocity in a given firearm for a constant set of loading components where only charge weight is varied is 0.992.
The only circumstances where this relationship fails are 1) if the barrel is too short for the application, i.e., unburned powder is ejected from the muzzle, and 2) load density is less than 70%.

So, can we not have someone with a strain guage AND a chronograph test this hypothesis? The test would compare pressure and velocity in a given rifle while only varying charge weight. Pressure at max book velocity should also be quite close to max as well, regardless of the charge weight given in the manual.

[ 10-30-2003, 21:10: Message edited by: Sabot ]

Sabot - would you have to figure a correction factor for actual barrel length vs. barrel length used for published data? The other item that you may need to figure is where the velocity reading is taken - directly at muzzle, 5 ft., 15 ft.

Every place that I have checked it, your hypothesis is true.

The problem, of course, is that you need both a strain gauge and a chronograph to establish the formula that links peak pressure and muzzle velocity for your particular rifle. Once you've set that up, you might as well take your pressure data directly off the strain gauge.

But in the cases I have tested, for a given set of components, in a given rifle, at the same operating temperature, peak pressure is linearly proportional to muzzle velocity.

I have to agree that velocity does not allways give a proper indication of pressure. I have found that in some cartridges, a point of no return is reached. That is where more powder does not equal more velocity. Also, I have seen the velocity drop off as the pressures became to high.

The big point here is, as was said before, every firearm is different, even in the same cartridge and caliber. Something to remember.

Jerry

Some of you seem to have missed the important qualifiers: Same components, same temperature, same firearm.

If you switch lots of powder, or change bullets, it's a different component. If you change rifles, it's a different rifle. Those cases are outside the stated question.

As you increase powder, pressure and MV increase. You will reach a point, though where MV will increase more slowly, and then stop increasing. Meanwhile, peak pressure continues to increase.

So you can't say that peak pressure and muzzle velocity are linearly related in all cases. But, in the hands of an informed user, MV is very definitely a useful pressure indicator for the same components, in the same rifle, at the same temperature.

As Dutch succinctly puts it, "Muzzle velocity is a pressure sign."

I have used velocity when working with a clearance powder ,but I caution ,the rifle barrel friction or constriction will give low velocity and high pressure.

Reloading with a chrony is to me only useful if Im doing it to compare one bullet type in one gun to accuracy vs. amounts and types of powders.Velocity that proves most accurate can be duplicated with different powders.Each bullet type goes through this.
I load for 3 guns, never have exceeded manual max loads and other than steady increases in velocity have no idications of increased pressure(bolt lift,primers, case heads etc.)Either I am lucky or others are loading well above manual data in which case they need one other very widely read book.

The velocity should depend on the area under the pressure/ time curve.
This varies with powder type of course. For the same powder (and every thing else) the peak pressure should should track the average pretty well.
Good luck!

In the real world, the correlation HAS to be virtually perfect.

Think of it this way. If pressure did not lead to velocity, how could a program like Quickload predict velocity as closely as it does?

Now, when you go OUTSIDE the norm; wrong size bore, grossly overcharged case, wrong burn speed powder, too light a primer, things are going to go nutty, once in a while, and a chrony won't save your bacon. Nor will anything else, for that matter.

However, if you go through a standard load work-up process, and use reasonable components in reasonable quantities, velocities will tell you what is going on, for the most part. Very inexpensively, easily, quickly, in real time.

As far as testing the hypothesis, I believe we are in the process of doing just that. JMO, Dutch

WELL...I am still stuck as on the one hand I have this data that supports the hypothesis and on the other anecdotal evidence and opinions that refute it. However, there is a lot of experience uot these so I give the opinions a lot of weight.

How about an example to clarify what the data say?

Say we are loading for a new 30-06 with 24 inch barrel. We have worked up a few loads, some near max, and the rifle seems to be working fine. Now we get serious, and set up the chronograph. We use Hodgdon data for H4350 and a 180 gr Sierra Game king bullet, noting that max is 57.5 grs, 2798 fps and 49,300 CUP.

The data I have from the DOD says we are better off increasing the charge weight to reach the 2798 fps than we are working up to 57.5 grains. The reason for this is that we could very easily hit 2800 fps at 55 grs, and 57.5 is too hot.

Now, if the reverse is true and we go to 60 grs to get 2800 fps many think that this is also a hot load. I admit that this is a prudent assumption as we are all cautioned to NEVER exceed a max load. I think this is the best rule for reloaders in general and it should be followed.

However, if you have a ballistics lab and you run into 2800 fps at 60 grains, you don't give it a thought, because you know the pressure is now max. At 57.5, it was a bit below max.

Look at your experience with Militery brass in rifles...heavy with less capacity. This drives pressure up, so the manuals say to cut back a few grains when working up. However, if you worked up to a velocity rather than a charge weight, this would be unnecessary. You would hit the max velocity a few grains early.

The same thing happens with bores and chambers. Even seating depth...Hornady recommends that you seat to the lands and then cut back a few grains as you will achieve max velocity with a lower charge weight.

Your max is not 57.5 grains nor 2798fps. Your max is 49,300 CUP.

Using your scale and chornograph, in conjunction with your pressute testing equipment, load to 49,300 if max pressures is your cup of tea. If you use more powder to get there, and your velocity is strange, suspect the pressure testing equipment. Use it as a check. Just because there is a maximum, are you held to have to load to it evey time? Is there a rule that says every load must be a max load?

[ 10-31-2003, 20:21: Message edited by: Nitroman ]

I like Nitroman's attitude. If you work for the DOD, you ought to be familiar with the saying "close enough for government work".

In other words, if you want to sharpen the pencil that much, you will need to use it to write the check for the pressure tester.......

Now, I like velocity as much as the next guy, but 100 fps has never made a difference, yet. JMO, Dutch.

Yeah, may be. You would think that metallurgy would have progressed right along with the testing equipment though.(?)

I don't believe that guns are being made out of substantially stronger stuff than they were 50 years ago. Buyers haven't been clamoring for stronger alloys, either.

Sabot, you are correct if the powders used are of similar burning rates. However, if there is much variation in this characteristic, it will NOT hold true! For example, if you load a .30/'06 with 150 grain bullets and enough Bullseye powder to produce 50,000 PSI, your velocity will fall short of that you would achieve by using IMR 4895 with the same bullets to produce the same max pressures.

Likewise, you will achieve much higher velocities in large volume cases by using slow-burning powders loaded to the SAME pressure levels as faster ones, like H4831 vs IMR 3031, etc! This is because the slower ones sustain a higher pressure on the bullet for a longer period of time as it travels down the barrel, even though PEAK PRESSURES are exactly the same.

[ 11-01-2003, 18:19: Message edited by: eldeguello ]

Another question I wonder about: How do you check the calibration of your chronograph? I know the usual suggestions to see if you're in the general ballpark by testing, say, a factory loaded .22LR, but there's considerable variation in what You'll see with those, too.

Sabot,

I've found what you say to be true, but others make good points as to the variables and such.

I've tested quite a few 308 WIN and 300 Ultra Mag loads and others too, but when you first hit the max MV "or" charge weight either one you'll usually find pressure signs after this point, there is exceptions but it's usually the rule.

Many times I have never hit "either" ones limit before encountering pressure signs, and sometimes as low as several grains below too.

One or the other is bound to be close near a max load, so the manuals aren't completely full of BS and are a pretty good guide for the most part.

Seating "on" the lands will usually put you a grain or three below the manuals max charge weight when you hit the manuals max MV, in this case I believe pressure is obviously higher to get the MV.

Just the other day I hit max load on the lands, and when I seated them .100" deeper, PSI and MV dropped enough I had to add 2 more grains to get it all back. 2gr more brought PSI and MV BOTH back to the same exact point also.

Hot Core,

When you see a Strain Gauge user quote a Load as producing 71,583psi, that person has no clue as to the Dangerous and Harmful effect that can have on a Beginner. If they did, they would never have posted it. Oh yes, I understand "Why" they do it, because they have convinced themselves (incorrectly) that their Strain Gauge Data is "Absolutely Perfect". However, it gives the Beginner the False Impression that they can actually Load up to that level on a regular basis, and everything will be fine. "So-and-so did it, my rifle is new(great shape, etc.) and I should be able to do it too. Obviously the Reloading Manuals don't know what they are talking about!" Totally WRONG - AGAIN!

First, you make an incorrect assumption that the person thinks his strain testing equipment is "absolutely perfect".

Next, you fail to see that any load manual that publishes data is no different than anyone publishing pressures and loads on a public forum. Both assume the reloader understands his gun is probably different, the reloader assumes all responsibility, and also uses "safe loading practices"...PERIOD

At some point, people in general, and reloaders alike have to take responsibility for their faulty "assumptions". You assume too much and ask too little, so I understand you may think everyone is like this too.

Keep running around intent on protecting foolish people from themselves all day long, but it reminds me of the gun control crowd... People kill people, guns don't... Fools and control freaks have a hard time understanding this concept, are you one of the two? If not, WHY do you waste your time?

Good day...

NotRicochet,

I've read BB guns and 22's. It's nice to have this option and most don't, but I happen to have an Oehler M43 and a 35P both and at times I'll set them one in front of the other, that's the best I've done for calibrating them. They both read within 3-5 fps of each other, and that's good enough for me to know one isn't defective.

One rail is faster than the other by probably 7-10 fps I'm guessing. If I set it up last in the series, it will read 3 fps faster than the first one, still. My rails have dimples in them for the set screws and I've just left them in the standard spacing and haven't fiddled with them to get them "exactly" the same. When I place the 35P down range to measure BC's I use the slower rail at the muzzle and the 35P at 500yds. 10 fps isn't much to the BC at that range, may be a BC change of .005 or so.

How do you calibrate a strain gauge system?

You read the gauge factor off the strain gauge, and enter it into the program. It is tested by the manufacturer, and known to three significant figures.

You read the amplifier gain off the interface box, and enter it into the program. This is also available to three significant figures.

The program supplies the physical properties of steel, which are well known, and very constant for rifle grade steel. You supply the inner and outer diameter of the chamber, which you can easily get to 3-4 significant figures with a simple dial caliper.

These are the only variables. When all are known, they combined in a well-known and thoroughly proved equation for hoop strain, that converts the number of microstrains read by the strain gauge to chamber PSI.

Your system is now calibrated to basic physical quantities, just as piezoelectric gauges are.

The landmark pressure studies done by Brownell at University of Michigan were done with a strain gauge. Incidentally, he learned strain gauges at the same place I did, Tektronix.

Barnes Bullets, one of those manufacturers with millions of dollars worth of equipment, uses strain gauge equipment to develop their published loads.

It works. Deal with it.

Shooting commercial ammo is simply a check to make sure you have done all the above correctly.

quote:

---

What you have to rely on at home is the accuracy of each of the elements in the system...the absolute accuracy of the system is probably pretty good, but nobody can say how good. In that case, it is wise to use it as though it gave only relative answers.
Varmint Hunter Magazine article, by me

---

[ 11-03-2003, 01:03: Message edited by: denton ]

Oh, by the way, nobody knows how accurate either the piezoelectric or the old CUP system are, either. What we know pretty well is the repeatability of the piezoelectric, CUP, and strain gauge systems.

If all rifles were created equal then I believe your hypothesis would be factual. But since they are not then such a hypothesis can only be taken at face value. Velocity CAN give some very strong indicators, but should not be taken as gospel in terms of pressure.

One very good example is some results I obtained from a worn out 8X57 recently. Pushing a 175 grn sierra behind 48.5 grns of Rlr 15 I had only obtained 2134 fs!! According to the hypothesis I should have had much more room to increase the powder charge but in reality that was not the case. 1/2 grain more and the velocities had jumped over 200 fs. I was rapidly nearing critical mass in a badly worn bore. Under normal circumstances the velocity will be a much better indicator of pressure than this, but I am just demonstrating one of the many variables possible, and although this was an extreme case, a lot of small variables can be enough to make the difference between perfectly safe and big trouble.

I believe that a handloader should learn and pay heed to as many pressure signs as possible, including reputable up to date data.

[ 11-02-2003, 21:05: Message edited by: Wstrnhuntr ]

WstrnHunter and I are in violent agreement. Use all dependable indicators available to you.

[ 11-03-2003, 01:04: Message edited by: denton ]

Sorry about the long post folks, feel free to skip it if you like.

Hot Core,

Originally posted by Brent Moffitt:
Keep running around intent on protecting foolish people from themselves all day long, but it reminds me of the gun control crowd...(Now, here's the part you left out of the quote.)People kill people, guns don't Fools and control freaks have a hard time understanding this concept, are you one of the two?

Originally posted by Hot Core:
Hey Brent, Taking your last response first, since you are "attacking me", I've apparently posted something you think is directed negatively specifically toward you. When looking back at the sequence of this Thread, I don't see it. But, I can respond to you in that way since it is apparently your desire.

I post PSI and MV from my rifles measured with strain gage systems and chronographs... you don't seem to like this practice. My desire is that you, as Denton put it, get over it. Respond to me however you like, but when "looking back on a thread" don't intentionally misquote me and twist the meaning of what I said, got it pal!
You might try "reading and comprehending" that again and also answering the question this time, but I doubt you will...

Originally posted by Hot Core:
Your premise that "your" Loads are as Valid as those from ANY Bullet or Powder Manufacturers Load Data Manual shows you are COMPLETELY out of touch with REALITY.

Originally posted by Brent Moffitt:
...you fail to see that any load manual that publishes data is no different than anyone publishing pressures and loads on a public forum.(Now, here's the part you left out of the quote, again.) Both assume the reloader understands his gun is probably different, the reloader assumes all responsibility, and also uses "safe loading practices"...PERIOD

I'm not sure what part about that you fail to understand, but any load, PSI and or MV that I or anyone quotes here or anywhere else on the net is usually stating these are what we got in our rifle, and our rifle alone. Any assumption you, or anyone else might make as to the our PSI or MV numbers being equal to the chamber pressures measured in load manuals is an error on your part, from another assumption I might add.

Originally posted by Hot Core:
For you to think your results from a few shots across a Strain Gauge are as "valid" as the Component Manufacturers Data is, is completely laughable and makes you look very foolish(stupid, absurd, ignorant, etc.) to anyone with even a few years of Reloading Experience. Let alone those of us who have done it for nearly five decades.

First, I'll say there are a few variables in strain measurements even when comparing factory ammo to reloads using a different lot of brass. Now, if even you reload the factory brass to the same indicated pressure using the same components, there are still variables left. Now compare those loads to the same load in a different lot of brass and that's another variable, so you've got a point.

I do however think the diffence is so small in most cases that it remains within 2-3K PSI for the most part. Valid as MFG's data is a good question. I think the tolerances in factory barrels, and the varying ballistics that come from them point to how accurate the MFG's data is when applied to "our" guns... That said, a strain gage on MY barrel IS even MORE accurate than a transducer in a pressure barrel or another strain gage on "different" barrel. This wouldn't be nearly as helpfull to me, that's my opinion FWIW.

This comes from experience checking this. What experience do you have with starin gage equipment that makes you an authority on them? As far as know, it's none...

I'm not even going into switching components, seating depth etc, and mentioning how helpfull strain measurements are in diagnosing problems or minute or major changes in ballistics, peak PSI is just one of the things it indicates, and no where "near" all of them.

Laugh if you want. Close your eyes to reality and technology if you want. Your loss, not mine...

Originally posted by Hot Core:
I do agree with your comment that at some point Reloaders must take responsibility for themselves. But, here again(as usual in any discussion you enter where you have little experience) you are missing the point. Look in any "What Chronograph should I buy thread?" and it is very rare to see anyone point out the "improper conclusions" that can be created by using a chronograph. You will see plenty of the "inferences" that Velocity is equal to Pressure which is TOTALLY WRONG. The only thing that seems to explain this is it happens because those folks don't realize it is WRONG to create this impression in the Rookie's mind

In most situations, velocity is a very good indicator of pressure. If pressure is off by a whole lot more than what would be acceptable at what is a known max MV for your gun with a given bullet, tell us all how we can get more MV with less peak pressure. Am I missing something here? In other words, if you're using an apropriate powder in a 26" barrel and MV is falling 200 fps slower than the manual states it should be at with this powder charge, I'm guessing you'd settle with 200 fps less MV and assume MAX PSI had been reached because max charge weight had been. What I'd think is really happening is PSI is low and MV is also low as a result, BUT before I'd exceed the book load to find out if that were the case, I'd have looked at every other PSI indicator at each step of the way to also help keep me out of the RED ZONE. You may not like the newbies to read what I do or my thoughts on this, but that is what I do and is what I think FWIW. I'm sure there's many who do stop at which ever comes first, either MAX charge weight or MAX MV the manuals recommend, and that's sound advice. You usually won't end up being 50-100 fps off from what they say even if you hit max load first, so how much does it really matter. If you want to squeeze every last drop of MV out of a cartridge, I say just get a bigger cartridge and operate at lower pressure while keeping MAX MV or better that the smaller one provided...

Originally posted by Hot Core:
I seriously doubt anyone recommending a chronograph to another person has any desire at all to see them get hurt with it. But to leave the impression that the use of a chronograph (or a Calibrated by guess Strain Gauge) can provide totally SAFE stand-alone information is flat WRONG.

Anyone who uses "any" method as a "stand alone" peak pressure indicator is foolish. A wise reloader uses several indicators to verify the other...
Even Piezo transducers systems have problems that strain gages don't and as a rusult must take 50 shot samples to be valid in SAAMI's eyes. That's just "one" reason Barnes and others have switched to strain gage systems to track peak pressures.

The "calibrated by guess" strain gage comment is another assumption from you as a result of your unwillingness to accept the accuracy of the strain gage systems. Again, your problem, not mine...

Originally posted by Hot Core:
Your last paragraph appears to be indicitive of your frustration at having someone point out the inherent problems associated with equipment "you think" makes you an Expert at Reloading. The thing that keeps a lot of older experienced folks from disagreeing with you though is your "mean spirited" responses to anything they have to say that you disagree with. Hopefully this response from me is in the same "mean spirited way" so you understand, but I doubt it. The end result being you don't receive all the input you really need that could help you mature as a Reloader.

I realize I'm wasting my time responding to you, because you apparently have a "reading comprehension" problem. I've wondered about that for quite awhile now but had it verified in the other Pressure Thread when you posted that you didn't know how/where to measure PRE/CHE.

I don't mind your so called "mean spirited" remarks, but what does ruffle my feathers and waste my time responding to is your incesent assinine assumptions and misquotes. If I come off as being ticked off, I probably am.

If you find my ignorance of PRE and CHE a result of my reading and comprehention inability, well that's another fine assumption on your part, your opinion and nothing more...

You don't know me and have no idea what level of experience I have other than what I've stated, so lets not even go there, pal. Some older gents have a big problem listening to a younger one, especially when it's contrary to what they believe, and it makes no difference if it's fact or not. I've lived long enough to know all 50yr old reloaders (for example) don't have the same level of knowledge, skill or wisdom when they've been doing it the same length of time, and this goes for more than relaoding too.

I'm simply here to share my experiences and knowledge if it might help someone else and to learn from other folks that share theirs as well...

If anyone disagrees with me, it wouldn't be the first time and I don't think it'll be the last either. I take the good and leave the bad, and am always open to criticism, unlike many. I'd have never learned much in life without the ability and willingness to do just that.

You point out problems with your "lack of understanding" of strain equipment, not my equipments inherant problems. People that "do" understand how it works and "have" used them will easily see this, those that don't and have not, probably will "not".

Originally posted by Hot Core:
For anyone interested, here is a Test to see if in fact Brent can read and comprehend:

So Brent, how do you Calibrate your M43 Strain Gauge System? And, how do you know when it is out of Calibration?

Denton outlined it to you as well as it gets, as it has been a number of times already...

I'll add that I use factory ammo when available for a referance. I can tell you that all I've really found with factory ammo is that the strain gage system indicates pressures that I'd expect with it. Believe it or not...

Originally posted by Hot Core:
I feel sure it will be of comic interest for other folks reading this Thread to see how Brent "knows for sure" his Strain Gauge devices are Calibrated. But, Brent will probably ignore the question - as usual - since his attempt at answering it would prove my point.

Comical to some, but it's calibrated as well as it gets, and makes no difference to me if anyone accept it as "enough" or not, to each his own. You've convinced yourself it's dangerous I gather, I just couldn't disagree more...

I have used them for quite some time to say this though. Have you?

[ 11-03-2003, 03:29: Message edited by: Brent Moffitt ]

In defending his beloved PRE and CHE methods, Hot Core wrote on October 27, 2003

quote:

---

In the example I used, it depends on the SAFE MAX Pressure determined by the Factory for that specific Lot of Cases. I don't know what the Pressure is in xx,xxxpsi, nor does it matter, because we STOP when we reach the same PRE as the Benchmark Standard from the Factory Ammo.

The Factories have millions of dollars ($$,$$$,$$$.xx) tied up in Test Equipment and Technicians to verify that they are producing SAFE MAX Loads. Here we get to use the information they provide for us, using First Hand information directly from their Case.

---

If I understand his statement correctly, he says that PRE and CHE are good, because they are based on a comparison to factory ammo.

Then, on Nov 1, 2003, he ridiculed the strain gauge system, saying

quote:

---

Even more confusing is when a Strain Gauge device is tossed into the equation. Reason being is they can't be "Calibrated". Just that simple. The only way to Calibrate a Strain Gauge on a firearm is to have Certified Loads from SAAMI. Of course, SAAMI "ONLY" supplies Calibration Loads to Ballistics Labs, so the average Reloader is out of luck.

That gets the person down to "guessing" about the Pressure reading from the Strain Gauge based on an "Unknown" Test Load.

---

Now if I'm understanding his statement correctly, he is saying (incorrectly) that the only way to calibrate a strain gauge system is to compare it to factory ammo, which is an entirely unacceptable standard, and that makes the strain gauge system bad.

So, Hot Core, could you perhaps enlighten us poor benighted souls out here. Which is it?

My response to all this is simple: I've done the experiments and math to know the repeatability of the Fabrique strain gauge system and the PressureTrace strain gauge system. I've researched, and done the math, and have found the repeatability of the old CUP system. I have published those results. I don't know the repeatability of the PRE and CHE systems, but, with like-minded people, I'm hip deep in an experiment to find out. If either method is good, we'll all say so. If they are not, we'll say that. Just the facts, ma'am.

I find only two questions posed.

Do I know the thermal characteristics of strain gauges? Yes. The cheap ones are far more temperature stable than most piezoelectric transducers. The difference between shooting on a cold day and shooting on a very hot day amounts to about 250 PSI, which is a very small error.

Do I believe that the amplifier is perfectly stable? Of course not. Modern instrumentation amplifiers drift as much as 50 ppm/degree C. That is a negligible error.

I am surprised that anyone with 20 years of experience with strain gauges would pose such questions.

An instrument is calibrated (accurate) when the mean reading of many observations equals the standard. An instrument is precise when the random error associated with its measurements is small.

By your ridiculous definition, the speedometer in your car is worthless because it is not absolutely correct, and the thermometer you take your temperature with is worthless for the same reason.

All measurement systems lie, at least a little bit.

What I can say with certainty is that the error inherent in a well-done strain gauge system is on a par with the best piezoelectric data available, and superior to the old CUP system.
We will shortly be able to make a statement on the quality of measurement available from the PRE and CHE methods. We will be able to do that, because we will have taken data and performed the correct analysis on it, something notably absent in your zealous defense of PRE and CHE, and your attacks on the strain gauge system.

By the way, I have two strain gauge systems, not counting being able to hook directly up to either of two fine Tektronix oscilloscopes. Neither system is Oehler.

I shot some Remington 165gr Scirocco factory ammo a while back in the 308 WIN and from the Oehler M43 was 58,0K PSI. On the other hand, the Federal 165gr SGK factory ammo only produced 48,9K PSI. MV was 2667 fps and 2594 fps respectively...

This rifle has a 20" barrel and the slower Sierra GameKing load is listed as having a MV of 2700 fps in the book titled "Ammo and Ballistics" by Bob Forker. If you really want to know the PSI those load develop in "test barrels" you could call Federal and Remington see, but I suspect both are pretty close measurements.

This I believe, goes to show all factory ammo isn't necessarily the best benchmark to go by, although it may all still be safe in our rifles.

Two more I took from the 300 Ultra Mag not too long ago were using Remington 180gr Partition factory ammo and it showed 62,9K PSI average and the Remington 180gr Scirocco factory ammo showed 60,3K PSI average, MV was also 3244 and 3180 fps respectively.

I certainly could purchace SAAMI referance ammo from Olin to calibrate the offset but the difference in barrels, etc, etc, etc would also corrupt this type "calibration" as well, so why? The numbers I get from factory ammo are at or just under SAAMI specs, and this is what I'd expect from a "looser" spec barrel.

Are we really splitting hairs here or what....

(I imagine this next statement will totally confuse some of the Strain Gauge folks, but this is the only way they could SAFELY be used.)

If the entire box of Factory Ammo was used to establish a Benchmark Standard with the Strain Gauges and if whatever the Strain Gauges record as the "Average Pressure in psi"(across the 20), then the Strain Gauges could be used to Develop Test Loads, but only up to that Benchmark Pressure. Since the REAL Pressure of the Factory Ammo is "unknown" the Strain Gauge user should not quote specific Pressures.

Hot Core, I looked back for a statement you made about using SAAMI referance ammo to be a valid measurement to calibrate strain gage systems with but that the ammo was only available to ammo MFGS, but I either missed it or you edited it out. Anyway, you should know as well as I stated above, if we did this they still would NOT be calibrated if the rest of the SAAMI protocalls were not exactly followed, which is near impossible nor is reasonable doable for a guy like myself. I'm sure you understand that absolute PSI measurement with any system is impossible as well. So the question is how close is close enough???

If you have shot all the factory ammo I have through several rifles, you might begin to understand how I could feel so comfortable with the numbers I get and the repeatability of them, the absolute accuracy of the numbers related to PSI must be real, real close or I'm just the luckiest guy alive. Never the less, I know they are relative to my rifle and not necessarily absolute PSI, but they do seem to be very, very near what one would expect for the cartridges I've tested. If this was not the truth, I'd never feel comfortable about using the strain equipment on the wildcats for which I have NO referance ammo as a guide, but simply the same barrel and case measurements taken in the same way I normally do. The amazing consistancy the system has proved in duplicating commonly published maximum pressures for the various cartridges is the "only" reason I feel the numbers are so close to actual, and I wonder if it's even worth splitting hairs over, that's all.

As far as quoting PSI numbers, the inferance is always there that the numbers are absolute, but knowing these measurements were not taken in a controled environment such as SAAMI does, they are not absolute, but there we go again, neither are SAAMI's numbers either, who's to say which of our numbers would be closer in all together different rifle with the same load.

One could argue that anytime someone gives a charge weight and MV without respect to the rifles throat length and COAL, that this is infering it's fine to load it up in your rifle because it didn't blow thiers up. We know that COAL and throat length has a minor to major effect on the maximum charge weight at a given PSI, at least I have data that proves this without a doubt.

There are so many things that effect chamber pressure, that every individual needs to be aware of "before" he or she jumps into reloading, this is their responsibility to learn these things, and is not mine to teach them. I'll help how ever I can, but just like most anything, including driving a car on ice for the first time, the responsibility is yours, and yours alone when "you" finally "choose" to do it.

One could also argue that if you teach someone something about reloading, you'd better teach them "everything" or you could be liable for what you "DIDN'T", which is BS, but it is still argued.

Life has become a "blame it on someone, for any reason, if at all possible" scenario in every way you can concieve, and personal responsibility, which I highly respect in anyone, or anyone who advocates it has simply fallen by the wayside.

I find it hard to agree with anyone that doesn't advocate personal responsibilty just as well, that's all

Hey Brent, Excellent post you just made.

Glad to see someone tossed a bucket of water on you to cool you down.

...

For what it is worth, I worked with a Mr. Flint that had 55 years in at a particular company and he refered to my Boss(Mr. Gysin) as a "Rookie" because he ONLY HAD 52 years in. Mr. Flint told me after a meeting (where I was beginning to get a bit heated, if you can imagine that), that the moment a person becomes mad in a discussion, is the moment they generally loose the debate.

I've not always been able to maintain my cool in a discussion, but I ALWAYS remember Mr. Flint's message.

[ 11-05-2003, 03:45: Message edited by: Hot Core ]