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Old April 10, 2013, 05:40 PM   #6
SHR970
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Join Date: January 24, 2011
Posts: 1,427
Quote:
dahermit wrote:So, those who have better credentials in the matter, or have done some hardness tests on the brass cups (seems that the hardness of the brass alloys could be measured on spent primers without too much difficulty), what makes Federal primers more sensetive than CCI; the priming compound or the cups?
There is a problem with the underlined idea. As you bend/ deform/ hammer brass it work hardens. Taking a spent piece of brass that has been deformed more than another will yield different results given that identical lots of brass are used. Now let us assume that the alloy and thickness between the Federal and CCI primer brass are both different. Let us also assume that the Federal brass is "flattened" and the CCI looks "normal". For argument sake let us also assume that the composition inside is the same and the same powder etc. are the same to remove these variables.

The Federal brass by being more flattened will have been deformed more and could test as similar to or harder than the CCI brass. One would then assume it is the thickness that is the culprit. But you still don't know for sure if the difference in alloys used work hardens similarly or differently.

To test properly you need to know a few things. First what alloys are used. You would also need to know original thickness of the sheet that the cups get made from (work hardening step number one is forming the cup) and if they anneal the material before or after punching the disks that the primer cups are formed from if at all. Then you need to know the final thickness of the cups after forming (if the disks are of differing diameters to begin with, to get a final cup thickness will be different even if the original stock was the same thickness). Then we need to test fire and record the pressure differences due to primer compound composition to see if there is enough difference to matter. This is not a complete list; it is just to highlight that simply using spent primers does not at all paint a good picture on why one primer type seems softer that another.

And in my experience Federal primers show do show pressure signs way before CCI, Remington, and Winchester.
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