Technical Articles

Peterson Cartridge Product Changes

 

At Peterson Cartridge Co. we really do listen to the feedback we receive from our customers. And we make improvements to our casings based on your recommendations. As a result, aspects of our casings change from time to time. Some of the changes could require you to revise your load for optimum performance at the target.

To keep you apprised of any improvements we make, we provide the below-listed chart, showing the different versions, and when they were instituted.

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Tight Primer Pockets

Internal Volume of Brass Case

Regarding the Peterson .308 family of casings, in large-rifle-primer size, your primer pockets seem tighter than others?

On the first firing of a cartridge, whether it is ours or most others, the primer pocket diameter opens up about .0007 of an inch. SAAMI spec for large rifle primer pocket diameter is .2085 to .2100.

Our pocket diameters start out .2075 to .2078. So prior to its first firing our primer pocket diameters are slightly tighter than the bottom of spec. If we started out at the SAAMI min diameter, after your first shot you’d be in the middle of spec, or higher depending on how hot your load is.

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Test Results On Peterson’s .300 Norma Casing

Internal Volume of Brass Case

At the 2017 SHOT Show a customer came to Peterson and expressed interest in a .300 Norma case that could hold substantially higher pressures than existing casings in that caliber. So that is what the development team at Peterson set out to achieve. And they did it. 

The cartridge is CIP registered, with a max pressure of 63,800 psi. Peterson’s customer wanted a casing that could withstand 75,000 to 80,000 psi, without the primer pockets loosening, or showing other signs of overpressure. In addition the customer wanted a standard deviation on the muzzle velocity as low as 10 to 15.

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For Optimal Performance You May Need To Change Your Load

Internal Volume of Brass Case

As you know, the exterior dimensions of rifle casings for any given caliber, no matter who makes the casing, are pretty close to the same. SAAMI, the US standards organization, specifies external dimensions, so anybody’s ammo will fit in any gun chambered for that caliber. However SAAMI does not call out internal dimensions. Internal dimensions vary considerably among casing makers. And as internal dimensions change, so does internal volume.

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