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CUP to PSI

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10 May 2007, 17:49
jro45
CUP to PSI
Does anybody know what 62000 CUP = in PSI? My 458 Lott has this much CUP shooting a 500gr bullet over 2300 FPS
10 May 2007, 17:56
Rusty Marlin
There is no direct translation and any translation you may find is really just a best guess.


Rusty's Action Works
Montross VA.
Action work for Cowboy Shooters &
Manufacturer of Stylized Rigby rifle sights. http://i61.photobucket.com/alb.../th_isofrontleft.jpg
10 May 2007, 18:19
vapodog
quote:
Originally posted by jro45:
Does anybody know what 62000 CUP = in PSI? My 458 Lott has this much CUP shooting a 500gr bullet over 2300 FPS

It's extremely doubtful your Lott is at 62,000 CUP as this (very loosely) translates to 76,000 PSI

BTW...Rusty's comments are correct!


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Winston Churchill
10 May 2007, 18:31
Rusty
I think 400 NitroExpress said it best. . .
quote:
The British standardized all of these flanged nitros a century ago in their base crusher guns - a methodology that no one else in the world ever used (and thus never understood), which isn't convertible to modern piezo values, and which Britain hasn't used since joining CIP in 1980, by which time this ammunition was no longer being manufactured in Britain.



Rusty
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11 May 2007, 01:27
ScottS
If your load is 62,000 CUP you had better back it off at least 9000 CUP! The SAAMI MAX AVG Pressure for the 458 Lott is 53,000 CUP as I recall.

Vapadog, I could believe a Lott loaded to 76000 psi +/-.
11 May 2007, 01:39
jeffeosso
55,000 roughly equals 62,500 psi... MORE OR LESS

jeffe


opinions vary band of bubbas and STC hunting Club

Information on Ammoguide about
the416AR, 458AR, 470AR, 500AR
What is an AR round? Case Drawings 416-458-470AR and 500AR.
476AR,
http://www.weaponsmith.com
11 May 2007, 01:58
jro45
I figured it up on a form I used all the correct figures. It is on the web. I certainly hope it is wrong. My 338 RUM has 65000 PSI but 76000 is alot more.
11 May 2007, 01:58
vapodog
quote:
Originally posted by jro45:
Does anybody know what 62000 CUP = in PSI? My 458 Lott has this much CUP shooting a 500gr bullet over 2300 FPS

I'd rather believe you meant 62,000 PSI and not CUP


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"Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery."
Winston Churchill
11 May 2007, 02:04
vapodog
quote:
Originally posted by ScottS:
Vapadog, I could believe a Lott loaded to 76000 psi +/-.

Aaahhhh....yea I know.....you must be talking about the .458 Lott AI animal


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"Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery."
Winston Churchill
11 May 2007, 02:08
invader66
A good read which tries to explain. Also see
Lyman Reloading.

http://www.shootingsoftware.com/ftp/psicuparticle2.pdf

Jeff,Hogkiller what do ya'll think of the graphs?


Semper Fi
WE BAND OF BUBBAS
STC Hunting Club
11 May 2007, 17:30
ScottS
Vapodog,
The 458 Lott AI is precisely what I had in mind. rotflmo
11 May 2007, 20:49
Rusty Marlin
[QUOTE]Originally posted by invader66:

A good read which tries to explain. Also see
Lyman Reloading.

http://www.shootingsoftware.com/ftp/psicuparticle2.pdf

[QUOTE]

I shall consider myself re-educated on this matter.
Thank you for providing and excellant link.


Rusty's Action Works
Montross VA.
Action work for Cowboy Shooters &
Manufacturer of Stylized Rigby rifle sights. http://i61.photobucket.com/alb.../th_isofrontleft.jpg
13 May 2007, 05:10
CMcDermott
Some of the problems with the analysis is that his 93% is effectively an average - look at the graph of SAAMI maximumx and see that some of the cartridges are on his line - and some are really far off, much more than just 7%. Even if you believe in this method and are trying to use some old loading data that gives a max of 50000 CUP for a rifle that you want a 60000 PSI load. You do the conversion of 50000 CUP and get 57891PSI, the error factor is +/- 7%. So your PSI number is actually a range from 53839 to 61943. So do you add more powder, thinking you are only at 53K psi, or do you use a little less to get down to a desired 60K psi? This is why ballisticians say NOT to try and convert CUP to PSI. Mathematics allows this, but real world engineering doesn't.