I recently received the following note from a friend overseas. Since the question and answer have broad applicability, I'll put them here for future reference. I'll try to take and post some pictures for this in the next week or so, but it wasn't really something I had planned and I'll have to scrounge up a camera with macro capability from a friend so it might take a while.
Hello Germán ,
I have enjoyed reading a few of your posts and articles about primers among other things. I read a post recently were someone has been seating their primers way too hard and after some measurements, it seems my big clumsy fists have been squeezing the primers a bit too hard as well, giving about .008" crush at least. On the rare occassion I have been able to test over a chrono, I had higher than expected ES, so I am thinking it could have been the primers jammed in way too hard?
I mainly use the Russian SRM and LR primers in my 6x47 Lapua and my .284. What sort of crush should we be looking for with these primers?
Thanks for any help, from Rod D.
Photo from the Remington website shows how the anvil will pre-compress the pellet on seating.
To continue a bit with the unfortunately non-numerical approach, if the primer loses its edge radius on seating and looks somewhat concave, that's way too much pressure. A bit of flattening is normal and correct, but like Goldilocks testing the bears' mattresses, there's too soft, too firm and just right.
A worthwhile test might be to try chronographing three sets of loads, one in which you stop as soon as you get initial resistance (legs at the pocket bottom) one where you crush mightily, and one where you add a slight pre-compression as described above. The Goldilocks test so to speak. I would be very interested to hear your results and will do the same test myself next time I chronograph something.
K&M Precision Shooting Products
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