QuickLoad vs Max Pressure in PSI?

steve4102 · August 21, 2011, 10:41 AM

I was messing around with QL the other day and found that it lists max pressure for the 7.62 x 51/7.62 NATO at the same pressure as the 308 Win 60+K psi.

Is this a misprint or an error? I thought the 7.62 Nato ammo was loaded to 50K not 60+K.

Jim Watson · August 21, 2011, 10:54 AM

The error is in the misconception that commercial .308 is loaded to substantially higher chamber pressure than military 7.62 NATO. It is not.

The Army is not a member of SAAMI and did not adopt the term "CUP" for pressure measurements by crusher gauge. So 7.62 pressure is determined by a crusher gauge but still reported in psi from where the gauge was calibrated by hydraulic pressure or dead load. Which gives a lower number than a piezoelectric transducer that is now taken as Gospel for "psi."
Put a 7.62 in a piezo setup and it will read (nearly) as high as a .308, which is what you see in Quickload.

August 21, 2011, 10:41 AM	#1
steve4102 Senior Member Join Date: December 23, 2005 Location: Minnesota Posts: 2,968	QuickLoad vs Max Pressure in PSI? I was messing around with QL the other day and found that it lists max pressure for the 7.62 x 51/7.62 NATO at the same pressure as the 308 Win 60+K psi. Is this a misprint or an error? I thought the 7.62 Nato ammo was loaded to 50K not 60+K.

August 21, 2011, 10:54 AM	#2
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 19,163	The error is in the misconception that commercial .308 is loaded to substantially higher chamber pressure than military 7.62 NATO. It is not. The Army is not a member of SAAMI and did not adopt the term "CUP" for pressure measurements by crusher gauge. So 7.62 pressure is determined by a crusher gauge but still reported in psi from where the gauge was calibrated by hydraulic pressure or dead load. Which gives a lower number than a piezoelectric transducer that is now taken as Gospel for "psi." Put a 7.62 in a piezo setup and it will read (nearly) as high as a .308, which is what you see in Quickload.