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**Mike Irwin** · November 4, 2012, 10:30 PM

IMR is not a company. It is a product line.

In 1976 Du Pont was manufacturing IMR powders, as they had been since the 1920s, or when IMR (Improved Military Rifle) powders replaced the then standard MR (military rifle) powders.

Powder lots and formulations change over time, as do sensibilities on what is, isn't, and should be safe loads.

In 1976, measuring chamber pressures was also QUITE a bit different. It was done with copper crushers, and was, in large part, and art of guesstimation.

Now days pizoelectric transducers and strain gauges are FAR more reflective of actual chamber pressures, and far more repeatable.

November 4, 2012, 10:30 PM	#4
Mike Irwin Staff Join Date: April 13, 2000 Location: Northern Virginia Posts: 41,388	IMR is not a company. It is a product line. In 1976 Du Pont was manufacturing IMR powders, as they had been since the 1920s, or when IMR (Improved Military Rifle) powders replaced the then standard MR (military rifle) powders. Powder lots and formulations change over time, as do sensibilities on what is, isn't, and should be safe loads. In 1976, measuring chamber pressures was also QUITE a bit different. It was done with copper crushers, and was, in large part, and art of guesstimation. Now days pizoelectric transducers and strain gauges are FAR more reflective of actual chamber pressures, and far more repeatable. __________________ "The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza Baby Jesus cries when the fat redneck doesn't have military-grade firepower.