Lightly Cratered Primers

[Henryrifle]

Curious what you all think about the picture below showing some primer cratering. In general, and I could be wrong, I thought cratered primers were caused by a sloppy firing pin to firing pin hole fit. Headspace issues could also be a contributor as could overpressured loads. I am not telling, I am asking.

This is not causing an issue but one of my actions is causing this:

These are Federal 210s and I tried those to see just how bad it might be as I think Federal's cups are the thinnest. It is the same when using my normal primer, CCI 200s. BR2s are slightly better but still have a raised circumference.

On this action, firing pin protrusion is normal at .051". Measuring the firing pin diameter with a micrometer shows approximately .0647". Using the inside jaws of a caliper (not a great way to measure but the only one available to me) shows the hole to be approximately .0680" for .0033" of clearance. headspace is ~.0015"

I am using a 28 lb firing pin spring and wondering if this could be a contributor to the raised edges. The firing pin is a normal factory firing pin - either heavy nor lightened in any way.

I don't think any of this is causing a problem. It is just different than other actions shooting the exact same load in the same chamber with the same components.

Thank you for your thoughts,
Hank

 

[butchlambert]

The primer is not flat indicating no high pressure.

 

[Straightshooter1]

Curious what you all think about the picture below showing some primer cratering. In general, and I could be wrong, I thought cratered primers were caused by a sloppy firing pin to firing pin hole fit. Headspace issues could also be a contributor as could overpressured loads. I am not telling, I am asking.

This is not causing an issue but one of my actions is causing this:
View attachment 1556265
These are Federal 210s and I tried those to see just how bad it might be as I think Federal's cups are the thinnest. It is the same when using my normal primer, CCI 200s. BR2s are slightly better but still have a raised circumference.

On this action, firing pin protrusion is normal at .051". Measuring the firing pin diameter with a micrometer shows approximately .0647". Using the inside jaws of a caliper (not a great way to measure but the only one available to me) shows the hole to be approximately .0680" for .0033" of clearance. headspace is ~.0015"

I am using a 28 lb firing pin spring and wondering if this could be a contributor to the raised edges. The firing pin is a normal factory firing pin - either heavy nor lightened in any way.

I don't think any of this is causing a problem. It is just different than other actions shooting the exact same load in the same chamber with the same components.

Thank you for your thoughts,
Hank

I get pretty much have the same results from my 6.5 PRC with Fed 210's. And I also have a factory spring and firing pin that protrudes ~.051. My primers aren't flat either, so I don't give it much concern.

 

[Jon Leary]

Obviously there is a small ring around the firing pin hole. The metal pushes in there when fired. Shouldn't hurt anything.

. .

 

[butchlambert]

Of course I'm a big fan of an .062 firing pin fitted to a bushed bolt nose. I just suggested that it wasn't over pressure. To measure your firing pin hole in the bolt you need precision gage pins.