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 Post subject: Max. Pressures in LUP and CUP
PostPosted: Thu Dec 17, 2009 12:51 pm 
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This falls under the should know, but don't catagory.
I know there is no conversion formula for PSI to LUP/CUP. I have always stayed at least 1,000 LUP units below max. PSI levels. Which leads to my questions posed to the "old school reloaders" here on the forum.

What really is the MAX. LUP for 12ga. (2 3/4" & 3") loads?

What is the MAX. LUP for 20ga.?

What is the MAX. CUP for 12ga.? and for 20ga.?

Please feel free to answer even if you don't consider yourself "old school" :wink: .



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 Post subject: Re: Max. Pressures in LUP and CUP
PostPosted: Thu Dec 17, 2009 4:19 pm 
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Best to let them fade away. First, CUP is for metallic cartridges and LUP for shotshell. If you're using old data stated in LUP, assume it's safe since we haven't heard about anybody being hurt by those published loads.

HOWEVER, the warning about staying with the published recipes and not substituting components applies in spades when using recipes recorded in LUP. That's because there is no direct conversion to psi, and when loads originally reported in LUP have been cross-tested with equipment that actually records peak psi, it seems the absolute number is invariably higher.

The SAAMI max recommended service pressure for 12ga is 11,500 psi. There is no "MAX LUP" since you can't directly compute the corrsponding psi. A recorded LUP of 10,000 might actually generate 11,500 psi. Stands to reason then (but not necessarily true) that any recipe with recorded LUP > 10,000 might exceed the SAAMI maximum of 11,500 psi. If you have a burning desire to know actual pressures, assemble 5 rounds and send them to Tom Armbrust with $25 and he'll measure them.


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 Post subject: Re: Max. Pressures in LUP and CUP
PostPosted: Thu Dec 17, 2009 5:39 pm 
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I realize the nature of the "old" LUP and CUP (some older Lyman listed shotshell loads are in CUP) data which could not record peak pressures like the PSI listed data does.

Let me restate my question another way.
What LUP standard or limit have others used/use for these older listed loads. Before we had piezo tested PSI data what limits were used? I understand these COULD be higher than SAAMI max. PSI. I am looking for a reference point.
As I stated above, I always stay at least 1,000 LUP units below max. PSI levels on listed loads. What I really would like to know is how others handle this situation when working with LUP listings?

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 Post subject: Re: Max. Pressures in LUP and CUP
PostPosted: Thu Dec 17, 2009 6:57 pm 
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My standard for using data either listed in LUP or PSI is the fastest load listed is treated as the maximum. If loading these I make sure what ever bushing I end up using does not drop over the published amount.

So as not to be overly concerned with the consistency of the powder drops, I normally pick a load 1 or 2 levels below the fastest load. I'll then find the bushing that is close. I'll find the bushing that is closest. Whether it is one that is less or over depends on the intended use of the load. Good example is my Handicap/long sporting load. I picked the bushing dropping on the plus side of Hodgdon's International listing for 1200 f/s 1 1/8 oz of shot.

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 Post subject: Re: Max. Pressures in LUP and CUP
PostPosted: Thu Dec 17, 2009 7:24 pm 
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I'm afraid I don't understand the "situation" you're dealing with. LUP data is obsolete for a reason...it doesn't relate true, instantaneous peak pressure. If I were really concerned about pressure, I wouldn't want a WAG, so I wouldn't rely on LUP numbers.

Here's why.

I have several vintages of “Handloader’s Guide For Smokeless Powders” by the IMR Powder Co.

In 1989 all of the shotshell pressures were listed as LUP.
In 1999 all of the shotshell target loads were listed as PSI while the field loads were still LUP.
In 2000 all of the shotshell data was listed as PSI.

By perusing data from 1989 and 2000, I was able to come up with examples of identical recipes tested by both methods:

In the 20ga Target AA Hull:

1989…W209 primer, 16.0 grains PB, WAA20 wad, 7/8 oz shot, 1180 fps @ 10,200 LUP
2000…………………………………………identical components………… ……1195 fps @ 11,700 PSI
In the 12ga Target AA Hull:

1989…W209 primer, 19.0 grains 700X, WAA12 wad, 1 1/8 oz, 1200 fps @ 9200 LUP
2000…………………………………………identical components……………… 1190 fps @ 10,800 PSI

And my favorite, in the 16ga (Win AA type) Compression Formed Hull:

1989…W209 primer, 20.0 grains 800X, SP16 wad, 1 1/8 oz, 1175 fps @ 8800 LUP
2000…………………………………………identical components……………… 1210 fps @ 11,000 PSI

For the identical loads, the “pressure number” increased by 14.7%, 17.4% and 25% respectively.


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 Post subject: Re: Max. Pressures in LUP and CUP
PostPosted: Fri Dec 18, 2009 1:07 am 
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Thanks Waverider I understand your method.

Mike, you won't use any LUP data at all. I was not aware that there could be as much as a 25% difference between a published LUP load and PSI. I figured that at least minus 10-15% would be fairly safe, but if the differences can be as much or more than 25% the LUP numbers are indeed useless.
Ok, that is what I was looking for. LUP listed loads are out. Thanks Mike.

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 Post subject: Re: Max. Pressures in LUP and CUP
PostPosted: Fri Dec 18, 2009 8:16 pm 
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Quote:
1989…W209 primer, 20.0 grains 800X, SP16 wad, 1 1/8 oz, 1175 fps @ 8800 LUP
2000…………………………………………identical components……………… 1210 fps @ 11,000 PSI

For the identical loads, the “pressure number” increased by 14.7%, 17.4% and 25%


There might have been a reformulation of 800X, that one has a change of 35 fps, the previous 2 were much closer in velocities.

AH HA, so the smattering of loads listed with LUP pressures are just oldies but goodies that they never retested with the piezo.



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