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Sidelock
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Sidelock
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28 grains of either Infallible or Ballistite was listed as a recommended load with 1oz shot in my 1913 LAC catalog. This seems to have been a 3 DE load. Even if that 12,600 pounds is PSI that's a lot of pressure, if it is LUP's its horrendous, more like a "Proof" load.
Miller/TN
I Didn't Say Everything I Said, Yogi Berra
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Sidelock
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Sidelock
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Yes, 28 grains would be a 3 1/2 Dram Eq. load of Ballistite http://books.google.com/books?id=97dJAAAAYAAJ&pg=PA57&lpg#v=onepage&q&f=false .. BULK..................................................... DENSE.............'E.C.'......DuPont...Schultze...Walsrode Green......Ballistite.Infallible 3 Dram....42...........36.5..............42................30.....24..............21 grains 3 1/4....45.5.........41................45................32.....26..............23 grains 3 1/2....49...........43................48................34.....28..............25 grains More pressure information here https://docs.google.com/a/damascusknowle...fUOZEFU/preview
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Sidelock
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Sidelock
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Like most things in this country--since, for better or worse, we don't have a govt proofhouse--the conversion from crusher to transducer measurements didn't happen all at once. (Didn't really happen all at once in CIP countries as either. And to further complicate things, at least some of those countries--including England--continued to mark their guns with crusher values, like 850 bar, long after they'd converted to using transducers. In fact they never used transducer-derived proofmarks. When they dropped the "bar" proofmarks in 2006, they replaced them with STD for standard proof and SUP for superior proof.)
Meanwhile, in this country, I have a copy of the Lyman Shotshell Handbook (Third Edition) from 1984. When I go to the reference section, I find a long discussion on pressure--and on the crusher method of measuring pressure. But at least all the pressure readings were listed as LUP and not psi.
Last edited by L. Brown; 10/28/14 08:08 AM.
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Sidelock
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Sidelock
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I don't think a reliable conversion is possible.The transducer measures the peak pressure,but cup/lup measure an average pressure which can have differing peaks for the same average.
Mike
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Sidelock
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Sidelock
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The Birmingham Proofhouse will provide figures to "compare" their old crusher bar values to SAAMI transducer readings. But agree it's not an exact science, and there's no mathematical conversion. However, if you have a measurement in bars or kg per sq cm, assuming they're taken with a transducer, you can convert to psi by multiplying x 14.5.
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Sidelock
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OP
Sidelock
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Thanks for all the info. I had read a lot of that, but not all. The conclusion seems to me to be that they could have published conversions, they just didn't choose to bother.
I am also unable to find any data on the effects of instantaneous high pressures, generated by a gas medium rather than a mechanical load, on modern steels. Only real world situation I can think of is firearms. I seriously wonder that at a level below the burst pressure that the steel doesn't react more like a crusher than a transducer, and that before the instantaneous peak can begin to produce the effects overstress on the steel, the peak is past.
I do know I have talked to some propellant engineers with a couple of the manufacturers, and I still use the old higher load data. When loading metallics I start seeing pressure signs at the same points I did 35 years ago.
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Sidelock
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Sidelock
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Can one reasonably infer that working pressures established for rifles made for the
7x57 cartridge translate to higher pressures measured with the modern PE method?
In other words are old rifles sturdier than one would think?
JC
Last edited by JayCee; 10/29/14 09:25 AM.
"...it is always advisable to perceive clearly our ignorance." Charles Darwin
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Sidelock
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Sidelock
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Can one reasonably infer that working pressures established for rifles made for the 7x57 cartridge translate to higher pressures measured with the modern PE method?
In other words are old rifles sturdier than one would think?
JC That's a loaded question, pun intended. I think a lot of them are/were, but... You could infer that, but I think a lot would depend on the rifle, the type of action, condition, and if you could get any kind of information on the steel(s) used. And who did the original testing, how, and how much do you trust that data. For some loads like 45-70, newer higher loadings have been developed for specific newer actions, but the 7x57 has been around a long time and most of those are bolt guns. I believe the recommended loading and pressures you see are suitable for all of them, but before I started building up loads until the primers were flat and I couldn't read the cartridge base I would want a lot more information.
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Sidelock
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Sidelock
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Without reference to any particular caliber, you will have higher readings with PE, than with crusher, because they are measuring different things. You cannot compare old "CUP" data to more modern "PE" data and make any assumptions about increasing or decreasing the powder charges.In other words, you will be asking for trouble if you exceed the accepted "crusher" derived maximum numbers in order to come up to the maximum accepted "PE" derived numbers.I used the term "numbers" instead of "pressure", on purpose,in an attempt(maybe misguided)to avoid confusion.
Mike
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Sidelock
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Sidelock
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Very briefly: LUP (Lead Units of Pressure) and CUP (Copper Units of Pressure) are both crusher methodology units. Due to the different characteristics of lead and copper, LUP was used to describe relatively low pressure cartridges such as shotshells, and CUP was used for cartridges that generated higher pressures (e.g. hand gun and rifle cartridges). The crusher methodology (regardless of whether LUP or CUP) provided a description of the entire area under the pressure curve. Transducer (piezo electric) methodology provides a trace of the entire pressure curve, as measured at a specific point in the chamber. The single value commonly reported as the transducer peak pressure is the highest pressure in that curve, as detected at the point of measurement. Crusher and transducer methodologies dont really measure the same thing. Thats why crusher and transducer pressure measurements can be neither meaningfully compared nor converted from one to the other. If you want more, see: http://www.saami.org/specifications_and_information/index.cfmP.S. I just have to ask. Of what are you an engineer? Well said. This entire thread belongs as a FAQ. Pete
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