Primer Pocket Specifications

[Nick Caprinolo]

Saami specifications for small rifle primer pocket depth, is .117 to .123.

I have new Lapua brass that measures between .122 and .128. I will uniform these pockets all to the same size.

My understanding is that the reason to unify the pockets. is so that all are seated at the same depth. As long as the firing pin strikes the primer with enough force, primer depth will not make a difference, as long as they are all the same. How deep is too deep?

 

[243winxb]

Flush to .008" below case head. SAAMI standard.

 

[Nick Caprinolo]

Flush to .008" below case head. SAAMI standard.

Yes that is the standard quoted by Saami. But what do you do when your primer pockets are deeper. How will it affect accuracy if you must cut them deeper than specs. My thinking is it really won't make a difference as long as they are all the same. That is what I am hoping to find out.

 

[INTJ]

Yes that is the standard quoted by Saami. But what do you do when your primer pockets are deeper. How will it affect accuracy if you must cut them deeper than specs. My thinking is it really won't make a difference as long as they are all the same. That is what I am hoping to find out.

I do this.....

https://kmshooting.com/product/primer-gage/

 

[jackieschmidt]

I do this.....

https://kmshooting.com/product/primer-gage/

I’m not sure what is meant by “seated to depth required”.

That should be firmly against the bottom of the pocket. Is an indicator need for that?

 

[INTJ]

I’m not sure what is meant by “seated to depth required”.

That should be firmly against the bottom of the pocket. Is an indicator need for that?

Ideally, we want .002" of crush for a small primer and .003" of crush for a large primer. For that to happen, each pocket has to be the exact same depth and each primer cup the same height. While we can get the pockets close, the primer cup heights vary. I have seen as much as .005".

This K&M Primer Gauge allows each primer, regardless of its cup height, to seat to that desired crush amount. When I started using this tool it did cut my ES by a few FPS in my BR rifle. I would not use it for a hunting rifle. I can seat two primers in just under a minute with the tool, but I don't have to do any other primer depth sorting after that.

 

[243winxb]

How deep is too deep?

Take a .128" deep pocket. Seat a primer. Is the primer more then .008" below the case head?

If yes, contact brass manufacturer.
If no, uniform all and seat primers.

The amount of firing pin protrusion should reach & fire primers deeper then the .008"

When the pocket is deeper then spec, the web may be thinner also.

Very old internet photo of web thickness.

 

[Clark]

hope this helps

 

[riflewoman]

an Excerpt from the SAAMI specs.