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 Post subject: LUP not PSI?
PostPosted: Tue Jul 07, 2020 6:35 pm 
Field Grade

Joined: Tue Dec 05, 2017 1:32 pm
Posts: 43
Looking at low pressure loads for my LCSmith. Hodgon is showing LUP on pressures below 8000 (Clays) Am I correct assuming LUP is Load Under Pressure. Why LUP
Thanks
Bill




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 Post subject: Re: LUP not PSI?
PostPosted: Tue Jul 07, 2020 6:50 pm 
Crown Grade

Joined: Mon Jan 23, 2017 9:08 am
Posts: 2254
Location: Central NH
Lead units of pressure.


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 Post subject: Re: LUP not PSI?
PostPosted: Tue Jul 07, 2020 6:54 pm 
Field Grade

Joined: Tue Dec 05, 2017 1:32 pm
Posts: 43
Thank you Painter. If I Google LUP it says add 1000 and that gives you the PSI


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 Post subject: Re: LUP not PSI?
PostPosted: Tue Jul 07, 2020 6:56 pm 
Crown Grade

Joined: Mon Jan 23, 2017 9:08 am
Posts: 2254
Location: Central NH
OldNWay wrote:
Thank you Painter. If I Google LUP it says add 1000 and that gives you the PSI

Google is generalizing. I don't think that's always the case.


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 Post subject: Re: LUP not PSI?
PostPosted: Tue Jul 07, 2020 7:02 pm 
Crown Grade

Joined: Sun May 17, 2015 6:25 pm
Posts: 2668
Location: On the wrong side of the river, Austin TX
LUP is an old pressure measurement based on how much a calibrated lead pellet was crushed by a piston that was powered by gas ported from a special pressure gun. Lead units of pressure is supposed to approximate PSI, and so is CUP, copper units of pressure where the pellet is made of copper instead of lead, used in measuring pressure in centerfire rifle rounds.

Today, piezoelectric strain gauges measure how much the chamber bulges under pressure and put out a reading in psi.
The pressure in LUP instead of PSI likely means it's old data from the time when LUP was the only way to measure shotgun chamber pressure.

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 Post subject: Re: LUP not PSI?
PostPosted: Tue Jul 07, 2020 7:05 pm 
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B.L.E. is right on. There is no reliable (consistently accurate) way to convert LUP or CUP to PSI.

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Last edited by Bob_K on Wed Jul 08, 2020 5:42 am, edited 1 time in total.

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 Post subject: Re: LUP not PSI?
PostPosted: Tue Jul 07, 2020 7:44 pm 
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Location: The U.P.'s U.P.
Three reading assignments:
On May 21, 2010 Shoot2reload wrote:
This one gets asked all the time. If we ever get an FAQ up and running, this needs to be in it! Here are a few threads to peruse:

https://www.shotgunworld.com/bbs/viewto ... 3&t=207744

https://www.shotgunworld.com/bbs/viewtopic.php?t=22760

https://www.shotgunworld.com/bbs/viewto ... =13&t=4724


--Bob


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 Post subject: Re: LUP not PSI?
PostPosted: Tue Jul 07, 2020 8:25 pm 
Crown Grade

Joined: Sat Mar 12, 2016 10:39 pm
Posts: 4794
Alliant has some loads less than 6,000 psi. Check their online reloading data. American Select is one of the powders used for low pressure loads.

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 Post subject: Re: LUP not PSI?
PostPosted: Tue Jul 07, 2020 8:53 pm 
*Proud to be a*
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Location: Central ND
B.L.E. is actually incorrect.

Strain gauges are used at the muzzle for certain pellet types. That was added to the SAAMI Standard in the 2015 revision of the Z299.2 shotshell performance.

Piezo-transducers are mounted in the pressure barrel 1" on centerline taken from the breech face. The 'pressure' reading is taken directly from the side of the hull. This has been the standard since 1992 when SAAMI went from lead crushers to the Piezo-electric system.

There is a system out there that uses strain gauges but they are not the industry standard.

Any question about what I have posted can be verified by checking out this link to SAAMI Standards:

https://saami.org/wp-content/uploads/20 ... -04-23.pdf

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 Post subject: Re: LUP not PSI?
PostPosted: Wed Jul 08, 2020 7:10 am 
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I do not load and shoot for a gun that needs low pressure. But if I did I would pick a different powder than Clays with the Hodgdon LUP data. And I load and shoot Clays exclusively for my 12 gauge needs.

One reason that the LUP units cannot be directly converted to Piezo-electric units is that they are a different measurement. The Piezo picks up fast spikes that are not seen by the LUP system.


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 Post subject: Re: LUP not PSI?
PostPosted: Wed Jul 08, 2020 8:37 am 
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Joined: Wed Nov 19, 2008 3:04 pm
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Location: Eastern Ohio
In my opinion LUP measurements are safe. I’ve never heard of over pressure loads due to it. We used them for years with out problems.

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 Post subject: Re: LUP not PSI?
PostPosted: Wed Jul 08, 2020 8:51 am 
Shotgun Expert
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dutch7373 wrote:
In my opinion LUP measurements are safe.


Measurements are not safe or unsafe... they are merely measurements.

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 Post subject: Re: LUP not PSI?
PostPosted: Wed Jul 08, 2020 9:03 am 
Crown Grade

Joined: Thu Dec 05, 2013 7:11 am
Posts: 4007
Location: Western Tampa, FL
As usual dogchaser37 is spot on! {hs#

I never heard the following question answered but maybe someone here can. Was the move to Piezo-transducer method done not only due to the better accuracy possible but because it was faster to set up and use and did not require "interpretation" like the older LUP and CUP methods did?

So was it not only easier to "read" the results with the newer Piezo-trunsducer method but also quicker to run more tests? If so, there would also be a cost savings in the newer method and would further explain the move to that technology.

I have a friend who will not use any data for loading that is not derived from newest test method. I say, regardless if the measurements taken by either method were within "specs" for the gauge; it should be considered safe to use. He loads almost exclusively for the 16 gauge, so encounters some of the older lead crusher method data. Am I wrong or does my friend owe me lunch? :lol:


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 Post subject: Re: LUP not PSI?
PostPosted: Wed Jul 08, 2020 10:15 am 
Shotgun Expert
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Location: Plainfield, IL
Quote:
The current method adopted by SAAMI for shotshell pressure measurement is to use the piezoelectric transducer system and then to express pressures so measured in pounds per square inch (psi). The old way was to use the lead crusher system and express pressures in lead units of pressure (LUP). While today all data regarding factory load shotshell pressures are measured and reported in psi, there is still some shotshell reloading data kicking around in which pressures are measured and expressed in LUP. Worry not. Both systems are valid.
- - - Tom Roster

Lyman discusses this in their reloading manuals. While valid, LUP cannot be accurately converted to PSI.

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 Post subject: Re: LUP not PSI?
PostPosted: Wed Jul 08, 2020 10:45 am 
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Clear up one thing for me. Is the LC Smith proofed for modern smokeless loads? Why load low pressure loads for it? Low recoil loads to minimize the chance of splitting the stock I fully understand and agree with. But why low pressure? Were these guns proofed to a different standard than what we use now?

I see a lot of interest in the low pressure loads. I am just not sure why? Is it a Damascus barrel?


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 Post subject: Re: LUP not PSI?
PostPosted: Wed Jul 08, 2020 11:37 am 
Crown Grade

Joined: Sat Feb 05, 2005 4:51 pm
Posts: 10856
Location: Phoenixville PA
8000 lup is a very safe load in your ELSI. Sounds like a very mild load.

LUP and the recent method given in PSI (gotten from a strain gauge hooked to an oscilloscope) don't give the same numbers and are not interchangeable, but lup was the method used until recently, and was considered fine.

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 Post subject: Re: LUP not PSI?
PostPosted: Wed Jul 08, 2020 12:14 pm 
Limited Edition

Joined: Tue May 03, 2011 1:25 pm
Posts: 311
Quote:
Was the move to Piezo-transducer method done not only due to the better accuracy possible but because it was faster to set up and use and did not require "interpretation" like the older LUP and CUP methods did?

So was it not only easier to "read" the results with the newer Piezo-transducer method but also quicker to run more tests?


Short answer - yes. The Unit of Pressure measurements required taking out the used pellet from the pressure measurement port, mic'ing it, translating the deformation into LUP or CUP, putting new pellet into port, sealing it back up. All that takes time. Transducers are ready to read when the next shell is loaded in the pressure barrel. And are conducive to electronic recording and automation of the testing process.

good luck, garrisonjoe


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 Post subject: Re: LUP not PSI?
PostPosted: Wed Jul 08, 2020 12:16 pm 
Limited Edition

Joined: Tue May 03, 2011 1:25 pm
Posts: 311
Quote:
Was the move to Piezo-transducer method done not only due to the better accuracy possible but because it was faster to set up and use and did not require "interpretation" like the older LUP and CUP methods did?

So was it not only easier to "read" the results with the newer Piezo-transducer method but also quicker to run more tests?


Short answer - yes. The Unit of Pressure measurements required taking out the used pellet from the pressure measurement port, mic'ing it, translating the deformation into LUP or CUP, putting new pellet into port, sealing it back up. All that takes time. Transducers are ready to read when the next shell is loaded in the pressure barrel. And are conducive to electronic recording and automation of the testing process.

And the current equipment will give a complete pressure curve over time. UOP measurement is max pressure peak during the firing only.

good luck, garrisonjoe


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 Post subject: Re: LUP not PSI?
PostPosted: Wed Jul 08, 2020 1:02 pm 
Crown Grade

Joined: Sun Mar 03, 2013 11:01 am
Posts: 6043
Location: Newton Kansas
dutch7373 wrote:
In my opinion LUP measurements are safe. I’ve never heard of over pressure loads due to it. We used them for years with out problems.

The only thing "wrong" with the LUP or CUP systems, was a lack of "time" information.

Since derforming a piece of metal takes TWO things, both pressure AND time, and time is extremely short in ammunition, the Crusher systems had a tendency to be accurate with "medium-burn speed" gunpowders, yet very fast powders could wind up a bit overpressure (but not massively) because their higher pressure for shorter time deformed the crusher the same as the "medium" powder did over the longer time.

This ALSO tended to leave very slow-powdered loads UNDER pressure, again, because less pressure, applied for more time, created the same crusher "pressure reading" as the medium burn rate powder did over it's shorter pulse interval.

The invention of the high-speed computer and the SAAMI chamber wall transducers, as well as the CIP and military direct pressure read transducers (read through a hole through chamber wall AND cartridge OR (military) hole bored through the barrel at the case mouth), are able to read BOTH pressure at instantaneous time intervals and determine what actual maximum pressures reached are from nanosecond to nanosecond.

In some cases, this has "detuned" (a little) old fast-powder loads which weren't "unsafe" (they weren't breaking guns) but were "over-specification limits".
It has also "boosted" some of the heavy loads (a little) which were not using the full range of available pressures as it was.

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 Post subject: Re: LUP not PSI?
PostPosted: Thu Jul 09, 2020 7:19 am 
Utility Grade

Joined: Tue Mar 20, 2018 6:46 am
Posts: 19
Thank you OLDSTUFFER. A good explanation.




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