Measuring Primer Depth with Calipers

[9.3x64]

I have always checked my primer seating depth with a pair of calipers using the depth function on the end of my Mitutoyo calipers. I don’t check every case, just the first few then leave it at that.
However using calipers to do this is extremely inconsistent, unless you have three hands. It can take a lot of mucking around to get repetitive results exactly the same because of the movement.
I just thought I would share a solution I have found in case someone might find it useful.
I ordered two Mitutoyo depth measuring spreaders . They are standard Mitutoyo accessories. They are made of cast iron and extremely heavy and stable. I use a large one at the rear of the calipers, and a small one at the front. I push the large one towards the case slowly, holding the primed case completely firm. The case doesn’t move at all. I have never measured primer seating depth so consistently. I measured three cases five times each, and got the same depth 15 times in a row.
I shave never had this sort of consistency before.
I hope someone finds this useful.

 

[ELR LVR]

Have you tried - with Caliper
Instead of trying to measure depth by utilizing the thumbwheel
Extend the depth gauge out firstly
Then set it against primer
and hold the caliper BODY
then bottom the outside anvils of the depth gauge on the case rim
The primer itself is pushing the depth gauge UP until it no longe can
only 2 hands required and should also give more repeateable results
--------
As opposed to you trying to extend the depth gauge against the primer
------------------
By using the above mentioned method - I get within .001"
of using a Depth mic

 

[9.3x64]

No I have not tried your method, but thanks for sharing.

 

[Mark611]

That's basically how I do it, Having a Machinist background and using these types of tools all the time makes it easy for me YMMV!

 

[Benchrest Braxton]

PRIMAL RIGHTS PRIMEWHERE KIT STEEL ANALOG - Graf & Sons

The PrimeWhere is Primal Right's new patent pending primer and primer pocket depth gauge. This tool allows you to precisely measure primer pocket depth, seated primer depth, and overall primer height. These indicators are produced for Primal Rights by the best drop indicator manufacturer in the...

www.grafs.com

 

[209jones]

I like using the depth mic better, more ergonomic, using the collapsing caliper probe works, I just find it awkward. I can set up the depth mic in a holder, and have one hand for the cases and one on the spindle, just watch the spindle and change the cases, goes PDQ. Find caliper awkward to manipulate, with the clutch on the depth mic spindle, I don't have to watch the case, then shift to read it in the same way.

 

[ShtrRdy]

Or there is this option:

Precision Primer Gauge

The Precision Primer Gauge takes precision measurements of primer pocket depth and the depth of seated primers in relationship to the face of the case head.

bullettipping.com

 

[nmkid]

Or there is this option:

Precision Primer Gauge

The Precision Primer Gauge takes precision measurements of primer pocket depth and the depth of seated primers in relationship to the face of the case head.

bullettipping.com

I had that tool, and it was consistent and very easy to use. As I no longer reload, I gave it to my nephew, and he uses it all the time.

 

[6BRA]

No way a caliper will give you consistent measurements where the cup seats in the pocket. Accuracy One or Rabbit Hole Precision. The caliper indicator will be in the center of the pocket. The center is not the same and outside where the primer cup seats.

 

[memilanuk]

Having had the Accuracy One device... I like the RHP one far better.

 

[9.3x64]

No way a caliper will give you consistent measurements where the cup seats in the pocket. Accuracy One or Rabbit Hole Precision. The caliper indicator will be in the center of the pocket. The center is not the same and outside where the primer cup seats.

That’s exactly my findings. If I hold the depth indicator on the edge of the primer, it gives a different measurement compared to holding the indicator in the center if the primer. This is why I put the depth indicator in the center of the primer and push the large weight to the primer.
It’s really simple, quick, and it’s consistent to 0.001 thou.

 

[47WillysGuy]

I use a magnetic base, dial indicator, and Wilson case gage to find primer seating depth.

Insert an unprimed case into the Wilson gage, measure the pocket depth, seat a primer and measure from case head to inserted primer.

You can see if your seating the primer fully to the bottom of the primer pocket.

 

[DocBII]

9.3,

Do you have a link to the parts?

Thanks,
DocBII

 

[47WillysGuy]

9.3,

Do you have a link to the parts?

Thanks,
DocBII

I assume you’re asking me for links to my dial indicator setup?

Sorry no!

But if you go to Amazon, and search my tool list, they have them all. Except maybe your particular Wilson case gage.

I use the indicator to check runout on case necks, just to verify straightness, also!

eBay may be a good source for used tools.

 

[9.3x64]

9.3,

Do you have a link to the parts?

Thanks,
DocBII

Hi DocBill,
I can’t find the links, but hopefully these two screenshots will give you the correct part numbers and the sellers details. I can’t remember which one was the larger one. Note that one of them has free delivery.
Cheers 9.3

 

[Webster]

I have always checked my primer seating depth with a pair of calipers using the depth function on the end of my Mitutoyo calipers. I don’t check every case, just the first few then leave it at that.
However using calipers to do this is extremely inconsistent, unless you have three hands. It can take a lot of mucking around to get repetitive results exactly the same because of the movement.
I just thought I would share a solution I have found in case someone might find it useful.
I ordered two Mitutoyo depth measuring spreaders . They are standard Mitutoyo accessories. They are made of cast iron and extremely heavy and stable. I use a large one at the rear of the calipers, and a small one at the front. I push the large one towards the case slowly, holding the primed case completely firm. The case doesn’t move at all. I have never measured primer seating depth so consistently. I measured three cases five times each, and got the same depth 15 times in a row.
I shave never had this sort of consistency before.
I hope someone finds this useful.

I don't care what the seating depth is. I seat to the bottom of the pocket by feel. My rifles shoot under .400" groups. If depth makes a difference you would probably have to be a HOF shooter testing in a tunnel. I consider it OCD reloading.

 

[Straightshooter1]

I don't are what the seating depth is. I seat to the bottom of the pocket by feel. My rifles shoot under .400" groups. If depth makes a difference you would probably have to be a HOF shooter testing in a tunnel. I consider it OCD reloading.

How do you know you're seating to the bottom of the pocket when seating by feel? OK, that you're getting very good results with the way you're setting them, but . . . you really don't know you're seating to the bottom, huh?

I question this because, a couple years ago I read a study that actually tested how seating by feel got primers to the bottom. . . or not. It looked at several different people using different tools seating their primers by feel. As it turned out, sometimes the primers were indeed seated to the bottom and lots of times they were not near as close as thought. It was inconsistent in terms of being on the bottom or not. This was done by taking detailed measurements. The study did not try to determine the effectiveness on velocity, accuracy or precision, just about how far primers were actually being seated. I found it a fascinating report.

 

[209jones]

I couldn't justify the price on the ones like the Rabbit Hole and Accuracy. Their not that much in US dollars, in Cda, add 30% + for exchange to start with, I used to calculate it double whatever the US price is, these days, could be more yet. Indicator would be a hair quicker, but, I'm not in a huge hurry when doing it anyway. Also, with using a uniformer to clean, I shouldn't have to worry about the pressure cup effect on the base, until maybe it gets too thin. So, the depth mic got the nod.

 

[JEFFPPC]

Still shaking my head and grinning.

 

[SeabeeKen]

I don't are what the seating depth is. I seat to the bottom of the pocket by feel. My rifles shoot under .400" groups. If depth makes a difference you would probably have to be a HOF shooter testing in a tunnel. I consider it OCD reloading.

Mine shoot .1" and any gain from primer seating depth precision is lost with wind and air density variations for me. I do measure pocket depth with the accuracy one tool. I spot check primer depth to satisfy my curiosity and it always within .0005" with my alpha brass. I also have deer rifles that shoot .1 or less and have nothing done to the pockets. My 6 RemAI shoots .027" for one