Primer compression

  • So the other day I was trying to work through my 7LRM brass "click!" issue and of my primers being seated fully came up.

    At the time I loaded them I used my coax because I didn't have the right shell holder so other than being 5 thousandths below flush, I didn't know where the primers in relation to the primer pockets.

    Well, I went and checked and found out that I was compressing the anvils about 6 thousandths.

    So now I want to know, what's the best way to seat the primers? Should they have the anvil just kissing the bottom of the pocket, have the cup on the bottom of the pocket or just be somewhere in between? Or does it even matter as long as they're consistent? Or is this something I'll need to experiment with to figure out?

  • I'm hesitant to give an answer here because I haven't done the kind of accuracy testing required to ensure the correct answer. So instead I'll tell you what I do: I measure the primer pocket depth. I measure the primer thickness to the top of the anvil. I measure the primer cup thickness.

    I make anvil contact with the bottom of the primer pocket, then I go an additional .002 to .004.

    Sometimes this will put primers flush with the base. Other times it will have them recessed as much as .008. It really all just depends on the brass and the depth of the pockets. I can't say if that is the best or not, but I've clearly had acceptable results.