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mrerick · 02-12-2019, 09:40 AM

Since the availability of lower cost strain gauge pressure instrumentation, I doubt many manufacturers rely on CUP copper cup crushing technology to measure cartridge pressures.

CUP is not only unrelated to modern PSI measurement technology, it is not linear in nature and doesn't even begin to provide the accuracy of PSI strain gauge measurements. As a mater of standardization, the SAAMI standard specifies both techniques for pressure measurement.

MegaPascal "MPa" is the metric measurement for pressure (Newtons per square meter), calculated using the same strain gauge instrumentation as "PSI" (Pounds per square inch). In a linear conversion one MPa = 145.0377 PSI.

235 MPa max pressure is measured with a different method using piezo strain gauge sensors. The method is not the same technique used by SAAMI, even though the type of sensor is the same. The method differences are discussed here:

https://en.wikipedia.org/wiki/Small_...#C.I.P._method

The NATO standard of 252 MPa measured in the SAAMI technique would convert to 36500 PSI. This exceeds the SAAMI 35,000 PSI max standard.

As to the 9mm Luger cartridge taper - I was not talking about taper crimp (which is what is used on a cartridge that headspaces on the mouth of the case) but rather the specification for the cartridge. A tapered 9mm Luger cartridge does indeed headspace on the mouth of the cartridge case, which is why you can never roll crimp the cartridge.

In the drawing, you can see that the 9mm Luger case outside diameter tapers from 9.96mm on the rim and 9.93mm at the cartridge body base to only 9.65mm on the cartridge mouth. The cylinder it fits in is also tapered up to the ridge that supports the case mouth. A Luger cartridge chamber is actually shallowly conical in shape, not cylindrical with parallel walls. This aids extraction.

If you look at the drawing of the 9mm Luger chamber on numbered page 27 of the SAAMI specification, you'll see that the ridge where the 9mm cartridge headspaces toward the front of the chamber is identified with a circle "X" symbol.

https://saami.org/wp-content/uploads...12-14-2015.pdf

02-12-2019, 09:40 AM	#17
mrerick Super Moderator - Patron LugerForum Life Patron Join Date: Dec 2009 Location: Eastern North Carolina, USA Posts: 3,900 Thanks: 1,372 Thanked 3,094 Times in 1,503 Posts	Since the availability of lower cost strain gauge pressure instrumentation, I doubt many manufacturers rely on CUP copper cup crushing technology to measure cartridge pressures. CUP is not only unrelated to modern PSI measurement technology, it is not linear in nature and doesn't even begin to provide the accuracy of PSI strain gauge measurements. As a mater of standardization, the SAAMI standard specifies both techniques for pressure measurement. MegaPascal "MPa" is the metric measurement for pressure (Newtons per square meter), calculated using the same strain gauge instrumentation as "PSI" (Pounds per square inch). In a linear conversion one MPa = 145.0377 PSI. 235 MPa max pressure is measured with a different method using piezo strain gauge sensors. The method is not the same technique used by SAAMI, even though the type of sensor is the same. The method differences are discussed here: https://en.wikipedia.org/wiki/Small_...#C.I.P._method The NATO standard of 252 MPa measured in the SAAMI technique would convert to 36500 PSI. This exceeds the SAAMI 35,000 PSI max standard. As to the 9mm Luger cartridge taper - I was not talking about taper crimp (which is what is used on a cartridge that headspaces on the mouth of the case) but rather the specification for the cartridge. A tapered 9mm Luger cartridge does indeed headspace on the mouth of the cartridge case, which is why you can never roll crimp the cartridge. In the drawing, you can see that the 9mm Luger case outside diameter tapers from 9.96mm on the rim and 9.93mm at the cartridge body base to only 9.65mm on the cartridge mouth. The cylinder it fits in is also tapered up to the ridge that supports the case mouth. A Luger cartridge chamber is actually shallowly conical in shape, not cylindrical with parallel walls. This aids extraction. If you look at the drawing of the 9mm Luger chamber on numbered page 27 of the SAAMI specification, you'll see that the ridge where the 9mm cartridge headspaces toward the front of the chamber is identified with a circle "X" symbol. https://saami.org/wp-content/uploads...12-14-2015.pdf __________________ Igitur si vis pacem, para bellum - - Therefore if you want peace, prepare for war.