The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Guns, Politics, Gunsmithing & Reloading Reloading Re: More About PressureTraceGo | New | Find | Notify | Tools | Reply | |
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Ah, Hot Core, you have once again twisted the facts beyond recognition, and resorted to name calling. Shame on you. If you are old enough to have "40 years of reloading experience" you are old enough to know better. I have not said that a scale cannot be calibrated. Quite the contrary, I said that it can quite satisfactorily be calibrated. Just read my post. What I said was, according to your definition of calibration, it cannot be calibrated. Since your definition leads to a conclusion contrary to fact, it follows that your definition is wrong. The fact that you so emphatically agree that a scale can be calibrated totally reverses your earlier position on calibration. Thank you so much! Somehow, I was sure you would do that, without realizing the implications. What you have just publicly, strongly stated is that it is acceptable to calibrate a measurement device with a standard that is not in the the same type of units that the device measures, as long as you know the conversion formula. That is something you have totally resisted until now. Hence, you can calibrate a scale, that measures weight, with a standard that is mass, as long as you know the conversion formula between mass and weight. w = m x g. You even thoughtfully gave us telephone numbers for people who will perform this service. So it follows that if I know the formula that relates chamber pressure to microinches of barrel expansion (which I do), and if I have a calibrated strain gage to measure expansion with (which I do), I can just as satisfactorily calibrate my strain gage system in absolute chamber PSI, with no other information. It is possible to trace every number in the chain to NIST, though I doubt anyone would go to the trouble. That bump you felt passing your teeth was your ankle. | |||
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Actually I just bought Pressure Trace, but have not had a chance to try it. I wish I could do the test you want, but I am using this on a muzzleloader. Not a whole lot of case measurements  edge. | |||
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Hot Cor, Thank you for the welcome. This should have been my first follow-up. You mention a micrometer measuring .0001, this would only measure the high spot. It would seem that an air gauge would be much more reliable, as you could measure the total distortion and not just the high spot, or one specific area. It is obvious that I am new to this board, and as a newcomer I question the vitriol? Or is this just good natured ribbing? edge. | |||
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Edge, When I asked my small children if that they were doing was "friendly fighting", they would always reply that it was, to keep me from interfering, so they would not miss a chance to poke the other one in the eye. | |||
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Quote: From Ken Waters himself:"A word about taking these measurements is in order here: I do not mark cases and attempt to position them just so in the chamber, as is sometimes suggested, measuring the diameter at that point alone. There is too much chance, I believe, that marked cases may be turned either in the closing of the bolt or in extraction. Instead, I revolve each case slowly between the thumb and forefinger of my left hand while I take a number of measurements with the micrometer held in my right hand. One point around the perimeter of the case usually produces a larger diameter reading because, at least in part, of the fact that gravity causes loaded cartridges to lie against the bottom of the chamber, inducing unequal expansion." I understand this to say, that taking one reading at a predetermined spot on a case is "the incorrect way" of measuring a case using CHE methods. | |||
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Some people believe Oswald was the only shooter. Some people believe the moon shots were done in a Hollywood soundstage. Some people believe the Earth is flat. Some people believe you can measure a fired cartridge case and accurately derive the conditions within that case when it was fired. | |||
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Hot Core Sorry you thought I was lost somewhere. I don't get to spend a lot of time on this or any other board. I'm quitting work early today. Only 16 hours. There are drawbacks to having your own business. What you do is pick the ammunition you want to use for a reference. Then you contact the manufacturer and ask them for the pressure specification for that lot of ammo. | |||
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Burt, thank you for those two posts. It seems to point in a direction my mind has wandered regarding strain gauge measurement of pressure. I suspect that all one needs to develop safe loads is a chronograph and consistent plots of strain vs. time. Reference ammo, precise measurements of barrel and cartridge case dimensions, etc., are not essential (sorry Hot Core). The factory ammo specs give us a velocity which we know some powder(s) can deliver at safe pressures. One could start with several powders from a single manufacturer (single base stick powders seem prudent) and see which of these delivers the lowest pressures as the velocities begin to rise toward the factory level. As the pressures rise, you can drop the powders too fast and too slow and concentrate on the two most promising canidates as you continue to increase the charge. Eventually, you get to the fps desired, and you stop and use the powder which gave the most favorable trace. By most favorable, I imagine one would look at max strain and how narrow the peak pressure area is. The beauty of this is that one need not have factory ammo to calibrate the system. You could even use this tedious approach to develop loads for cartridges for which factory ammo no longer exists. One could also do this with octagon barrels, for which theoretical equations relating strain to pressure aren't available (unless you have a finite element solver handy). Again, it is essential to have consistent strain measurements. By this, I mean the offset and scaling factors need to be very nearly the same from time to time. Even this can be checked by creating one's own reference ammo, a load which you can fire from time to time to verify the strain traces are still the same. It sounds, Burt, as if you folks know the business. The 4-layer board is reassuring. Digital hash always seems to enter the analog side of any simpler layout. I also like that you don't filter the samples in a effort to make a prettier plot. I'm still amazed you folks can offer the package for the price you do. I only have one rifle for which reliable load book data does not exist. Fortunately for me, the case capacity under the seated bullet is almost identical to some modern cartridges, and the good folks at Hodgdon and Lyman were nice enough to give pressure readings for their reduced loads. This (I believe) allows me to select an appropriate powder to use -- along with my chronograph. Enough! Bwana-be: I hope you try an RSI rig. It sounds like good fun. Karl | |||
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Quote: Hey denton, I sure don't remember joining any threads where I discussed "Calibrating Scales" or providing a definition of how to Calibrate Scales. If somewhere I ever said that a Scale "can't be" Calibrated, then I do agree with you and stand corrected. If you can provide a link to that post, I'd sure appreciate it. However, if perchance you "made-up" that I said Scales can't be Calibrated, that sheds a whole new light on your dubious character. The words Clintonesque and outright Liar come to mind. And it speaks voulmes for the way your parents raised you. ... Anyway for all you other folks, if I said "Scales can't be Calibrated", that was indeed as wrong as thinking denton knows anything useful concerning Strain Gauge Devices.  | |||
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Hot Core - your name seems well chosen: there is something vulcanic in your your mails. At this stage of the dicussion, calibration has been ventilated enough, IMHO. If you find your personalized calibration considerations needs more words, please do it by e-mail. Denton will be pleased to read your further elaborations. I for my part have a scale, well calibrated or not - I trust it, and I am content with the curves produced by my PressureTrace - I don't need further comments on calibration and Dentonism. Thank you. | |||
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Hey edge, Yes indeed, the muzzleloader was not what I had in mind. Which then brings up the obvious question of how a person could ever "Calibrate" the Strain Gauge Device(SGD) on it? In the Instructions that came with your SGD, was there any mention of Calibration? Quote: The only "Air Gauges" I've used measured the "inside" of a tube. When measuring PRE, you are measuring the outside of the case, so a 0.0001" capable Micrometer works very well. Quote: I think it depends on the people involved. I much prefer good natured ribbing and learning from people who have actual first-hand experience that I don't have. When I don't know something, I've no problem at all saying so. And when I have a different experience base, I don't mind sharing it. For example, Clark knows more about "blowing-up" firearms than I ever will, because he does a lot of it - intentionally. It interests him and I do enjoy his occasional posts about how a particular firearm failed his overloads. And there is no doubt in his posts that they are "overloads". On the other side, you have a few immature fools who claim a lot of things that are misleading at best and at worst just aren't true. Most of the time, it doesn't matter because it is either so outlandish that folks figure them out quickly and ignore them. Occasionally one will come along who seems to have some useable info, but you soon realize not only is that person FULL OF BEANS, but they can also be a "danger" to the Rookies who just don't know any better. Let me give you an example from the old "Shooter's" Board. Lots of "Rookies" would make a post similar to, "I need a HOT Load for a 165gr bullet in a 30-06." OKShooter was the first person I knew who had an Oehler M43. I thought I could learn some very useful info from him. But, he would make posts like this: In a 22" 30-06 I recently tested, 165gr bullet and xx.xgr of IMR-4350 got 3100fps at 72,358psi(M43). Here his reference to the M43(which is an excellent machine, as it sounds like Burt's is) gave "misleading credibility" to an "overload". The Rookies soon believed that since the M43 said 72,358psi and it was OK in his rifle, that they could also use them SAFELY in their rifles. And, he even posted loads of 100kpsi. OKShooter is the same guy I referenced above when I said, "He could never understand you could not get use Neck Sizing when doing PRE Testing". He is the first person I tried to work with to see how well CHE/PRE works when compared with a SGD. I phoned back and forth as well as emailing with him directly for a year and he kept getting very strange PRE measurements. He eventually told me he was "still Neck Sizing" during the Testing. I do remember there was no "good natured ribbing" in my posts to him after that. Some "wanna-be experts" just don't normally handle someone pointing out their misleading info which can get a Rookie in trouble. You see them try to justify such foolishness with comments such as, "Well, they should know better. or We can't include a Disclaimer with each post." Of course, the Rookies don't even have enough knowledge base to know posts like that can get them in trouble. I try my best to give it out as good as I get it. The big difference is, all my posts are based on first-hand experience, or if I don't know, I say "I'm guessing that...". And anyone can normally duplicate what I post very easily without having to spend and arm and a leg to do it. ... Anyway, best of luck with your SGD and as I said before, "Welcome Aboard!" | |||
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Hey T/C nimrod, I will not be criticizing Ken Waters. He is the man when it comes to Reloading. However, my post indicates what has worked the best for "me". If you have good luck with the method Mr. Waters lists, by all means go with it. If you find the CHE data to give wide variation using that method though, try what I suggested. | |||
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Quote: Hey Burt, I hear you and completely understand. I tried your suggestion about 5 years ago with Fed, Rem, Win and Speer and got something similar to, "All our ammunition is at or below the SAAMI specification!" Now, that is not a direct quote from them, but words to that effect. However, I'll give it another shot. Have you had better luck on getting specific Pressure Data and it's Range of value from them than that? | |||
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Quote: Hey waitaminit, I do understand your "heart-burn". Only problem is, I intend to keep posting on this Board. Rather than "telling you what to do", let me make this suggestion - look on the left edge of your screen. When you see "Hot Core" as a poster, just scroll right on by and my posts will not be a concern to you at all. Best of luck to you! | |||
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Quote: Hey Karl, No problem on my end. I work with all kinds of folks and "I suspect" some otherwise knowledgeable people just draw the "wrong conclusions" occasionally. Best of luck to you! | |||
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Quote: Quote: I'm confused - CHE must be done precisely, but it's open for interpretation? I'm having a hard time picking the correct information out of this thread. Just when I think I have something down pat............... You are correct, the original "test" was marred - but the specifics were ironed out between all those involved off board. | |||
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Quote: Of course, you never mentioned scales in particular. You spoke of calibration in general. I have consistently held that it is acceptable to calibrate to a standard that is different units, as long as you know the conversion factor. On this thread, and the previous one, you have consistently held that the one and only way to calibrate anything is to compare with a standard in the same units. I could provide quotes from the previous thread, but this quote from this thread will fill your request: Quote: Or are you saying that this is a special rule, that only applies to strain gages, and not to other measurement systems? Or that it is a special rule that applies to all measurement systems except scales? Quote: Well spoken. I rest my case. | |||
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Quote: The only "Air Gauges" I've used measured the "inside" of a tube. When measuring PRE, you are measuring the outside of the case, so a 0.0001" capable Micrometer works very well. We use Federal Plugs & Rings (ID & OD), with their 060 tooling you can have a part Min/Max of +- .0060 and a gaging of .00005 ( 50 millionths). With the muzzleloader, I am mainly interested in finding powders that will burn efficiently. The RSI unit with a chronograph should work perfectly. I am not looking for exact pressures, although the barrel ID and OD dimensions would certainly get me into the ballpark. I am more looking for gross changes in pressure from powder to powder, and bullet weights. I just don't want any surprises, and this would appear to be a prudent approach. So far Lil'Gun holds the most promise, but some had said that it may have some unwelcome pressure spiking, Pressure Trace will be "just the ticket" for finding out if this is true or not. edge. | |||
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I'm a kinda curious fellow and might even be considered a "Rookie." So one question comes to this curious mind. Why are there several systems on the market for the express purpose of measuring pressure in firearms and a micrometer is just called a micrometer. I would think they would just call a micrometer a firearms pressure tester and package it up as such with Hot Core's instructions. | |||
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"When you see "Hot Core" as a poster, just scroll right on by and my posts will not be a concern to you at all." Hot Core, it's my impression that you know a lot and know to put it into words. Actually, I like to read your mails, but the flaming, the flaming... I did not suggest you stop writing on this board: write as much as you want and whatever you want, but stop attacking other board members - it falls back on you - and it isn't a pleasure to read. As I see, you and Denton decided to continue the calibration wrestling, which is,IMHO, o.k. as long as it is done in decent, not injuring manner. I only suggested to post your erupting sentiments by e-mail. | |||
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edge.... Your suggestion to use an air gage is very intriguing. LOTS more resolution than a micrometer. | |||
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Quote: Hey waitaminit, Guilty as charged! Thank you for sticking with your point long enough for it to "sink in" past the irritation. You are correct. In fact, I don't enjoy seeing other folks trashing each other. Seems to be a good bit of that on the Gunsmithing Board right now. And I agree, it reflects bad on them as well. I'd appreciate it if you would remind me of this in the future "IF" you notice me lowering myself to that level again. A very sincere - THANK YOU SIR!!! | |||
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Quote: Hey T/C nimrod, I understand the confusion you are facing due to my post. First off, let me be emphatically clear that I would NEVER be critical of Ken Waters. Use Mr. Waters' method and forget what I posted about how to do it. That should totally clear up the "confusion" for you. ... When "I" use that particular way of measuring CHE(multiple point averaging), I've not had what appeared to be data as good as the method I outlined. I was taught the way I outlined by some of my Elders many years ago, long before I read Mr. Waters excellent writings. | |||
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Quote: Hey edge, Man-O-Man, now that sure would be nice to be able to tote along to the Range and get data significant to one more significant figure. Might be a bit awkward toting the Air Compressor though.  I guess they could still be used if the Casehead was measured before going to the Range and then once again after the trip. And they should be excellent for the PRE. Do you recon I could get a useable Air Ring Set for $21 like I can the Micrometers? (Only kidding.)... Lil'Gun in a muzzleloader? Are you using a Savage? | |||
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I have used Endevco,B&K and MicroMeasurements equipment. I have installed strain gages and calibrated strain gage systems. Its been awhile. The biggest concern about installing strain gages is gluing them on and not ruining the bond with the soldering iron. A small air pocket under the grid will wreak havoc with the actual values. When applied correctly with a thin bond line my experience tells me your going to be within 5% assuming you use a high precision shunt resistor to verify the amplifier.But its the one you didn't get right that will bite you. I believe proper bonding technique can be as difficult as some reloader using a .0001" micrometer and getting the correct diameter on the pressure ring as in the other method described. It would be interesting to send a cartridge and micrometer around to all that posted and see what they measure. Case head expansion will depend greatly on the yield strength and design of the cartridge case head. Along with the rifle design. The more the case head is supported by the barrel the less likely a diametral reading would correspond to and actual pressure. To illustrate the point take a reduced capacity case where the back 1/2" of case is solid with nothing but a small hole for the primer flash and see how much expansion is achieved for a given load. My point being you need to know about the case head design of the cartridge to know how much expansion is too much. Some cartridges utilize steel. Both methods being utilized are not meant to be emperical measures of actual pressure but to be used as indicators as to when you have pushed your load far enough. The system with the greatest potential is the strain gage system as long as calibration can be done. I would expect you can reduce alot of error in the system by applying pressure with a hydraulic hand pump to 10,000 psi. and make a calibration curve. Any ideas on how to do that easily may advance this discussion to a more constructive level. | |||
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Quote: These low resolution plugs and rings are in the 200 dollar range. Initial set-up is a couple of grand. Yes, this is for a Savage 10ML-II muzzleloader. edge. | |||
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Quote:Did I miss something or did Hot Core ever demonstrate his familiarity with Strain gages? Few months of absence, return to see the same song by the same players. I'm resigned to being plain dumb because I can't figure out why "calibration" via factory ammo is okay with PRE/CHE but not with Strain Measurement? Quote: DemoSam, Harold Vaughn wrote of his home brewed Strain Measurement rig (not nearly as nice as the RSI or even the Fabrique Scientific) in his book, "Rifle Accuracy Facts". He detailed how he calibrated with a hydraulic gage. Quite interesting - but probably not within the capability of most home hobbyists. | |||
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Demosam: In his "Rifle Accuracy Facts" Harorld Vaughn describes how he calibrated (true use of the word) a strain guage set up with a hydraulic set up. He also discusses errors involved with using dimensions, and gauge factor to measure pressures. This is the best "gun" book that I have ever read. Good luck! | |||
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This is just a general question on the subject. Aren't all rifles enough different that a precise pressure( calibrated or not) is not that important, but how MY particular set-up reacts to the pressure it sees? It would seem that to use a strain gage while ignoring other pressure signs would be as foolish as looking in a loading manual and using the MAXIMUM loading first! From my point of view, the RSI unit is a relatively inexpensive tool for looking inside the rifle as it is fired. Even if I do not calibrate the strain gage to anything, it WILL show me the shape of the pressure curve. It certainly will show the length of time that pressure remains high, and that may be more important than the actual magnitude of the pressure curve. edge. | |||
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Quote: That is absolutely correct. You effectively have a very nice digital storage oscilloscope, with excellent stability and high gain. My particular interest is in peak pressure, and I tend to pay the most attention to that. That is not everybody's interest. As pointed out, the shape of the curve is also interesting. Sometimes, you can see the point at which the neck tension releases the bullet, for example. I've never yet seen the erratic spiking associated with reduced loads of slow powders, but, if that happens, you should see it quite well. Also, it is not necessary for a measurement system to be absolutely calibrated to be useful, as long as it is repeatable. The RSI unit is very highly repeatable. When I work up a load, I make two cartridges at each of several powder levels over the range of interest. I fire them in ascending order, and chart pressure vs charge, MV vs charge, and MV vs pressure. With 6-10 cartridges, I have a good idea of how the loads will perform. Then it is just a matter of finding which load in that range gives best accuracy. Another interesting output of the system is the risetime of the pressure peak. The RSI does that from the 25% point to the 75% point. I'm so accustomed to 10% to 90% that I have to stop and rearrange my thinking for a moment, but that's OK. It gives you a number you can successfully compare to other powders and loads. | |||
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For everyone enjoying this Thread, let me reference another Thread currently being discussed on the Gunsmithing Board concerning Bolt Thrust: http://www.accuratereloading.com/ubbthreads/showflat.php?Cat=&Board=UBB5&Number=543349&page=0&view=collapsed&sb=5&o=2&fpart=2 "Varmint Al" has done some extremely interesting Testing concerning this issue and the whole Thread is an interesting read. However, I copied the second page because of some interesting pictures Varmint Al has included. If you take a minute to study them, it will become fairly clear "why" you have PRE. And the picture sure shows clearly where it occurs. ... Hey T/C nimrod, I've been thinking about my last post to you concerning "how" to go about doing the CHE. Let me make this suggestion, do it both ways. By that I mean measure the case across the "P"(for an example or any Reference Point) Before and After Firing, and record those measurements. It will only require that you measure and write-down "two additional" pieces of data. Also use that measurement as one of the "Randomly Selected Points" that you will Average in accordance with Mr. Waters directions. I believe you will find taking the "Reference Point CHE data" will be easier for you all to get the "same measurement" as the cases move through your group. The "Averaged Random Point CHE data" could possibly show a slightly higer variance since no two of the people taking the measurements are likely to measure the exact same points around the Casehead. ... Hey edge, I've heard some excellent things about the Savage Muzzleloaders from a pure performance standpoint. I did not realize you could use anything other than IMR or H-4895 in them. Best of luck with the Testing - to both groups. | |||
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Quote: See that's were you are losing me. I don't see Waters instructions as taking multiple point measurements and averaging them. I believe, (and I may be off), but I see him turning the case 360 degrees taking multiple measurements and documenting the largest measurement. He is taking the point of largest growth on a case as the maximum measurement. In other words if he sees .0002" of growth in 4 spots on a given case but measures one spot(a 5th spot) at .0003" - he documents the .0003" measurement, not the .00022" average of the five readings. Like I say, I may have been doing this all wrong for quite some time. That's why I'm here now, to learn my options (and weed through all the BS). | |||
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Quote: Hot Cor, Powders used range from Bullseye, for plinking loads, to AA2015! The two most popular powders are VV N110 & Hodgdon Lil' Gun. The velocities in the Savage manual are no higher than those touted by Knight and T/C with magnum loads of Triple 7, BUT THERE IS ZERO CLEAN-UP !!! and that makes all the difference. edge. | |||
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Quote: Hey T/C/nimrod, OK, try that. I completely agree with turning the case and looking for the High Spot when measuring PRE. Using the multiple point measurements on the Casehead may mean you accidentally skip-over the widest point. The other option is turning the Casehead inside the Micrometer Anvils to locate the High Spot. ... By the way, I'm so used to doing the measurements, that it is easy to forget a few things that could goof up your data. One problem that can skew the results a good bit(it can on the Reference Point method too) - the Extractor "might" create a burr along the inside of the Rim on "non-Belted Cases". If you do not have "Thin Blade" Micrometers so you can measure the CHE across the Web, be careful that your regular Anvils are not actually measuring the Rim. On a Belted Case, you simply measure CHE across the Belt with regular Micrometers. If the Anvils hit the Rim on a non-Belted Case, it is best to "File" down the Rim slightly in two spots across from each other so you can get to the Reference Point. Or if going for the High Spot per Mr. Waters, you will need to file the Rims down slightly all around. This is a whole lot of work and unnecessary if you all have the Thin Blade Micrometers. I got my Thin Blade Micrometers for $25 at a Pawn Shop. | |||
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The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Guns, Politics, Gunsmithing & Reloading Reloading Re: More About PressureTrace
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