Ideal primer pocket depth?

MTGunner

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Sep 24, 2004
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409
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Ronan, MT
Surely this has been discussed to the max. But, need input regarding primer pocket depth for Hornady brass for 7MM Remington Magnum. BTW, I use an RCBS primer hand seating press along with a Sinclair primer pocket cutter. I clean each and all pockets after each firing. MTG
 
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The main thing is the pockets are uniformed before you seat them. I see pockets that have a slight curve where the walls meet the floor, and need removal otherwise the primer anvil will not seat flush. From there it's best to be able to feel it bottom out. I use a Lee ram prime on a RCBS Partner press. I tried a larger press and it was too much or too little. Depth of primers ? If I stopped cutting the pocket when I reached the floor after the curve disappeared then they are uniformed enough for me. I go by eye...and actually measured them within a thou.
 
The concave bottom that the factory punches is the BEST shape the primer pocket can be….a flat bottom impedes gas flow….but you can do as you like.
If talking how far a primer needs to be seated…..well there is no such thing.
It is the amount of crush AFTER the cup and anvil are flush with each other that matters the most. This "cushion" and " pre-tension" affect the primer ignition the most and is what makes a primer ignition across the entire batch the most consistent.
If this is .004" crush, then that's what it takes to get that brand primer to ignite the same each time. Seating depth must be measured first, then crush and then experimentation with crush after that. A 10 round group of each crush amount will then determine the best crush.

Cheers.
 
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