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Double Rifles, Single Shots & Combinations >> Double Rifles

Tom_Bigbore
.224 member

Reged: 16/01/04
Posts: 44
Loc: Germany

Re: TPI, CPU, PSI
22/03/05 10:27 PM

Mike,
It is not that there is a difference in conversion of pressure units. The problem is a difference in the method of measuring. tpi means that the pressure has been measured with a copper ring at the base of the cartridge. Then cartridges have been tested with a copper piston at the side of the shell. When you measure the same cartridge this way, it does not show the same pressure. The difference is not linear or a fix data, but depends on a lot of influencies. It is around 17%. (plus/minus.. to give you an idea)

Nowadays, at least in Europe and other CIP countries, the cartridges are tested at the side with a piezo element. The piezo element shows higher peak pressure at the same cartridge as it works “mass free”. Therefor some pressure data given for a cartridge have changed. This change is only related to the method of measuring and does not change the real pressure inside the cartridge.
So here you find our problem. You can not be 100% sure that a load developed today is within the pressure limites for an old gun with data given in tpi. You just cannot measure it the same way. (or do it the cheap ;-) way as Graeme did)

Hope that helps
Tom

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Subject	Posted by	Posted on
TPI, CPU, PSI	AussieMike	22/03/05 05:57 PM
Re: TPI, CPU, PSI	KWK	25/03/05 12:16 AM
Re: TPI, CPU, PSI	unspellable	31/03/05 09:50 AM
Re: TPI, CPU, PSI	KWK	01/04/05 07:09 PM
Re: TPI, CPU, PSI	unspellable	03/04/05 03:22 AM
Re: TPI, CPU, PSI	KWK	03/04/05 11:21 AM
Re: TPI, CPU, PSI	AussieMike	04/04/05 06:15 PM
Re: TPI, CPU, PSI	KWK	05/04/05 12:06 AM
Re: TPI, CPU, PSI	unspellable	05/04/05 03:40 AM
Re: TPI, CPU, PSI	KWK	05/04/05 11:54 AM
Re: TPI, CPU, PSI	unspellable	05/04/05 10:46 PM
Re: TPI, CPU, PSI	KWK	31/03/05 10:44 PM
Re: TPI, CPU, PSI	unspellable	31/03/05 11:28 PM
Re: TPI, CPU, PSI	Tom_Bigbore	22/03/05 10:27 PM

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