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Shooting & Reloading - Mausers, Big Bores and others >> Big Bore Rifles
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Altamaha
.333 member


Reged: 29/12/08
Posts: 376
Loc: Washington State USA
Re: 458 Winchester Magnum Question
      18/12/09 02:57 PM

The universal receiver ( a heavy duty single shot, lanyard fired, with a quick disconnect barrel arrangement) is the standard machine used for proof testing ammunition in the ammo makers labs. And the standard barrel length for the universal receiver is 30 inches. In the past the barrels were fitted with a copper cylinder system to indirectly measure chamber pressure. (the machines are now fitted with piezoelectric transducers.) Copper cylinder crusher method could give inconsisitencies, as the copper cylinder was crushed by a steel piston that pierced the chamber wall. After firing, the length of the compressed copper cylinder is measured, and the pressure required to do this is either calculated or read from a "crush chart". Just think how accurate the pressures are if the wrong alloy copper was used!! This is why you will see CUP listed in the pressures for the old system, such as 54,000 CUP. It is not the same as a true PSI reading. CUP is Copper Units of Pressure. True PSI is generally thought to be more than CUP, so our 54,000 CUP might actually be 61,000 PSI or more.

Way back when the 458 was developed, CUP was used, so who knows what the real pressures were? Could have been lower or higher than reported. Using the universal receiver and the CUP system required a substantial amount of operator skill. Something like not properly cleaning the chamber and the steel piston would give incorrect numbers.

So this is why many of the published velocities for ammo are higher than what we mortals obtain with our chornographs. Longer barrel generally equals a higher velocity, but not always.

Note to handloaders: If using old manuals, be aware of the CUP listings, the manual should explain this.

Edited by Altamaha (18/12/09 03:02 PM)

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Subject Posted by Posted on
* 458 Winchester Magnum Question LFOD1776 06/09/09 07:04 AM
. * * Re: 458 Winchester Magnum Question 458ONLY   17/12/09 10:10 AM
. * * Re: 458 Winchester Magnum Question bwananelson   17/12/09 11:35 AM
. * * Re: 458 Winchester Magnum Question Tatume   17/12/09 11:55 AM
. * * Re: 458 Winchester Magnum Question bwananelson   17/12/09 01:25 PM
. * * Re: 458 Winchester Magnum Question Indy   04/11/09 02:17 PM
. * * Re: 458 Winchester Magnum Question bipbigbore   18/11/09 09:51 AM
. * * Re: 458 Winchester Magnum Question DUGABOY1   08/09/09 09:34 AM
. * * Re: 458 Winchester Magnum Question 4seventy   29/12/09 02:46 PM
. * * Re: 458 Winchester Magnum Question Ripp   29/12/09 03:00 PM
. * * Re: 458 Winchester Magnum Question 458ONLY   30/12/09 08:18 AM
. * * Re: 458 Winchester Magnum Question DarylS   30/12/09 03:55 AM
. * * Re: 458 Winchester Magnum Question bigmaxx   30/12/09 04:10 AM
. * * Re: 458 Winchester Magnum Question 4seventy   17/12/09 01:55 PM
. * * Re: 458 Winchester Magnum Question Altamaha   18/12/09 02:57 PM
. * * Re: 458 Winchester Magnum Question 4seventy   18/12/09 06:59 PM
. * * Re: 458 Winchester Magnum Question 450_366   18/12/09 07:40 PM
. * * Re: 458 Winchester Magnum Question bonanza   08/09/09 10:07 AM
. * * Re: 458 Winchester Magnum Question 9.3x57   08/09/09 11:49 AM
. * * Re: 458 Winchester Magnum Question KILLERtj   06/10/09 02:39 PM
. * * Re: 458 Winchester Magnum Question bonanza   06/09/09 07:26 AM
. * * Re: 458 Winchester Magnum Question Tatume   06/09/09 08:02 AM
. * * Re: 458 Winchester Magnum Question tinker   06/09/09 08:19 AM
. * * Re: 458 Winchester Magnum Question *DELETED* *DELETED* grandveneur   06/09/09 09:01 AM
. * * Re: 458 Winchester Magnum Question controlled_feed   06/09/09 10:46 AM
. * * Re: 458 Winchester Magnum Question bonanza   06/09/09 01:34 PM
. * * Re: 458 Winchester Magnum Question bonanza   06/09/09 01:40 PM
. * * Re: 458 Winchester Magnum Question LFOD1776   06/09/09 11:52 AM
. * * Re: 458 Winchester Magnum Question bonanza   06/09/09 02:04 PM
. * * Re: 458 Winchester Magnum Question LFOD1776   06/09/09 11:30 PM
. * * Re: 458 Winchester Magnum Question tinker   07/09/09 12:20 AM
. * * Re: 458 Winchester Magnum Question controlled_feed   07/09/09 09:01 AM
. * * Re: 458 Winchester Magnum Question ozhunter   07/09/09 05:42 PM
. * * Re: 458 Winchester Magnum Question 9.3x57   07/09/09 11:12 PM
. * * Re: 458 Winchester Magnum Question DarylS   19/11/09 02:49 AM
. * * Re: 458 Winchester Magnum Question Sarg   07/09/09 06:38 PM
. * * Re: 458 Winchester Magnum Question tinker   06/09/09 01:32 PM

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