My primer seating method

[Bronsin]

I have been using the K&M Primer Gauge for a while now. It allows seating each primer to an exact crush in its specific pocket. It saves having to measure each pocket depth and each primer cup height.

I haven't yet experimented with varying seating depths. I seat SR primers with .002" crush and LR primers with .003" crush. I do intend to do do some tuning with primer crush.

I also wonder if sorting cases by primer depth is worthwhile to test. Getting an exact crush seems to be the main thing, but making sure the firing pin fall to the primer is exactly the same might be worthwhile also.

I find up to .004" to .005" variance in primer cup height/pocket depth. I suspect that our uniformed pockets have a little variation, and I know primer cups vary in height.

I use the same tool and found that my "feel" with other tools was far more than .002 crush. When I uniform primer pockets, it's with the Sinclair tool that always cuts to a fixed depth. You can always sort primers according to their height to control that variable as well.

 

[INTJ]

I use the same tool and found that my "feel" with other tools was far more than .002 crush. When I uniform primer pockets, it's with the Sinclair tool that always cuts to a fixed depth. You can always sort primers according to their height to control that variable as well.

I have used many primer pocket cutters and currently use the K&M. Since I use the K&M Primer gauge I don't have to measure pockets or cups, but I am suspicious that a cutter spinning in a drill is going to cut pocket depths to with better than .001" variance by indexing off the case head. How hard we hold the case could cause that much variance.

I do agree that the K&M Gauge does show
how inconsistent our feel is. A tight pocket takes more force than a looser pocket to get the same crush.

 

[BORGY76]

How is everyone measuring primer pocket depth, and pockets diameters? What is your method for measuring "crush"?

 

[Dusty Stevens]

How is everyone measuring primer pocket depth, and pockets diameters? What is your method for measuring "crush"?

If you use a cutter and it cleans it up you can measure how deep it is. You can also measure a slug like i showed in post #1 and a depth mic to measure it

 

[sqrlgtr]

I have been using the K&M Primer Gauge for a while now. It allows seating each primer to an exact crush in its specific pocket. It saves having to measure each pocket depth and each primer cup height.

I haven't yet experimented with varying seating depths. I seat SR primers with .002" crush and LR primers with .003" crush. I do intend to do do some tuning with primer crush.

I also wonder if sorting cases by primer depth is worthwhile to test. Getting an exact crush seems to be the main thing, but making sure the firing pin fall to the primer is exactly the same might be worthwhile also.

I find up to .004" to .005" variance in primer cup height/pocket depth. I suspect that our uniformed pockets have a little variation, and I know primer cups vary in height.

^^^^ This is the best way I have found that takes the guess work out of it, and it did show up on target. I do uniform all my primer pockets to same depth and sure INTJ does also (I may have missed that in post if he said he did). It did show up on targets and I have piece of mind in that all primers are seated the same or as close as can be. Of course if your shooting a 1 moa rifle you probably not know the difference, I will go out on a limb and say I know you wouldnt be able to tell the difference..... I was using the old style lee priming tool before I went to the K@M tool and thought I had a pretty good feel for seating,,, pun intended....

 

[BORGY76]

If you use a cutter and it cleans it up you can measure how deep it is. You can also measure a slug like i showed in post #1 and a depth mic to measure it

So you are measuring depth from the face, not floor thickness? I guess I could see arguments for both measurements depending on where case mfg calls the datum.

 

[Dusty Stevens]

So you are measuring depth from the face, not floor thickness? I guess I could see arguments for both measurements depending on where case mfg calls the datum.

From the headstamp is the only place to measure pocket depth

 

[mikecr]

So you are measuring depth from the face, not floor thickness? I guess I could see arguments for both measurements depending on where case mfg calls the datum.

Why would anyone measure floor/web thickness?
It's unrelated to primer seating.

For a desired crush setting the pocket depth and uncompressed primer height needs to be zero'd out with each particular pocket/primer/rim. Then measure taken -while seating.
Ideally, this puts primer face consistently just below flush +/-a thou, with your head spacing consistent to a thou. With this, you could then test & adjust striking for optimum with a chosen primer/load.

Anything else is just making primers go bang.

 

[BORGY76]

Why would anyone measure floor/web thickness?
It's unrelated to primer seating.

For a desired crush setting the pocket depth and uncompressed primer height needs to be zero'd out with each particular pocket/primer/rim. Then measure taken -while seating.
Ideally, this puts primer face consistently just below flush +/-a thou, with your head spacing consistent to a thou. With this, you could then test & adjust striking for optimum with a chosen primer/load.

Anything else is just making primers go bang.

Well my thinking ( not a case mfg) is the explosion inside the case propels your projectile out of the neck and down the pipe. With some volume inside the case left for ignition the heat and pressure forward cause shoulder growth correct? Your primer pocket is movable just like the shoulder, which is why I was asking about measuring depth or floor thickness. I'm just getting into reloading, so most of my questions probably seem dumb to the masses.

 

[Dusty Stevens]

Well my thinking ( not a case mfg) is the explosion inside the case propels your projectile out of the neck and down the pipe. With some volume inside the case left for ignition the heat and pressure forward cause shoulder growth correct? Your primer pocket is movable just like the shoulder, which is why I was asking about measuring depth or floor thickness. I'm just getting into reloading, so most of my questions probably seem dumb to the masses.

Youre thinking about the combustion volume not really the timing of the vibration it takes to ignite that combustion chamber. The primer seating all matters for pre-ignition, case volume matters for combustion tuning which is what i think youre referring to

 

[group therapy]

No it takes into account depth of pocket and height of primer and gives you a variation reading. I auctioned one off on here a few years ago

 

[6MMsteve]

Have y'all did a test with this method vs your other extremely low cost method? Did you observe any difference in accuracy or MV SD?

Here is my method
View attachment 1348422

I use it for AR stuff it's quick but gotta be easy with it, it will break into a few pcs, ask me how i nos