Witch Doctor: Brief Follow Up to Primer Seating Depth Tests 

Question. Are we talking .008 below the base of the cartridge or .008 crush AFTER the anvil touches the bottom of pocket?

I'm unclear as to what your testing deemed important. Is it primer depth below flush with the case head (this is I believe the spec that SAMMI refers to) or is it the amount that the anvil is pushed into the cup? In your example these numbers are the same at .009" but that is only occurring because both primers, the BR2's and the 450's are the same thickness as the cups are deep at .122". In both examples the anvil is touching the top of the pocket just as the cup gets flush with the case head. Looking at the SAMMI specs for pocket depth and primer thickness you can see this isn't going to occur very often. The brass primer combination I'm currently using the primers have to be .005" below flush before the anvil even touches and I can't compress the anvil. 009" because it only protrudes .005" to start with. That said, this combo shoots well at .008" below flush. Thanks for any feedback you can provide. Also, do you define "crush" as the amount the anvil is pushed into the cup? Thanks

How deep are your primer pockets?

I need a seating depth priming tool. If you were in the market now, would you still go with the PMA? Is seems like a good value that will give consistent seating depths.

Hi Bryan, I ran across your channel a couple of days ago and really appreciate the videos you have posted. I watched all 3 primer seating videos and was hoping you would answer a question for me. I have measured my ADG brass for the 6.5 PRC. The primer pockets are 0.127-0.128 deep. When I measure the Fed 215M primers that I use, they are also 0.127-0.128 from the bottom of the cup to the top of the anvil. It looks like the cup itself is only 0.114 high which would make the anvil protrude about 0.014 above the cup. I know the only accurate way to find the proper crush is by testing but was curious if you thought that your testing results of 0.009 depth would apply here also? TIA

Bryan I have found your videos extremely helpful and informative. Can you tell me what you use to measure how deep the primer is seated in the case? Thanks

I use CCI Small Magnum primers in 6.5 Creedmoor Lapua brass. Would 0.008 likely be the optimal depth for it as well?

Good stuff man, thanks for sharing your testing.

Thanks and happy new year Bryan! I have been wondering about how primer seating depth and bullet seating depth may interact with barrel harmonics to drive different group sizes. For example,considering that 8 tho primer depth result in smaller group sizes than 6 tho at a given bullet seating depth, would we find opposite results with a bullet seating depth optimized for smallest group size at 6 tho primer depth? The theory behind it would be that primer seating depth impacts how the barrel vibrates when ignition occurs and selected bullet seating depth is optimized for the bullet to exit the muzzle at the right time for minimum/consistent vibration (i.e., small group size). I would be surprised if this theory would hold. But if it were, this would mean that different primer seating depths result in similar group size as long as the bullet seating depth is optimized for a chosen primer seating depth. Perhaps another test? Run a bullet seating ladder with the primer seated at 6 tho and check how group size compares with previous results?

Quite interesting!

This is really interesting. I use Lapua Blue box 6br brass and cci450 primers. The primer pocket and the primers are BOTH .120. In order to seat them .008 deep(crush) it takes a tremendous amount of force on both my Lee and RCBS primer tools. I ran the same test that you ran and for me that is clearly the worst depth. .003 was far and away the best in my rifle. Perhaps the point is twofold. First is that there definitely is a "best" and "worst" depth and second that each rifle and/or load will be unique in what it likes.

Primal Rights (the competition primer seater guy) has been talking about the importance of the timing of the firing pin hitting the primer. He’s basically talking about the distance from the firing pin to the base of the primer as the important measurement. Do you have any testing looking at timing vs the amount of anvil compression? Timing or the distance from the firing pin to the base of the primer would only seem to change the speed at which the firing pin hits the primer. I don’t know this as a fact but a couple thousandths of an inch would probably be almost the exact same firing pin velocity. Changing the initial amount of anvil compression by a couple thousandths would seem to make a much bigger difference in how the primer reacts. This is just my guess though. Depending on which one is most important would significantly change where the best place to measure from is.

Happy New Year Bryan!!!

Hey Bryan, have you done any seating depth tests with large rifle primers such as the BR2? If so, what level of crush on the anvil do you recommend? Love the videos, and thank you.

Awesome stuff!!

Are your primer pockets the same depth?