"Reading" primers for pressure.

[Moose83]

So... how reliable is reading primers as a sign of pressure? I keep reading on here about "flat" primers being a sign of higher pressure, yet other sources I've read indicate that primer condition has no correlation to pressure signs, flattened primers are more of an indication of chamber dimensions (I may be mis remembering this part). Case in point... I loaded 5 rounds of .243 with the 95gr BT starting at 40gr up to 44gr of Accurate 3100. All 5 cases primer condition was identical... flattened. Bolt lift and extraction on all 5 was easy and smooth, but the 44gr load looked like it had a very slight ejector swipes. What says Rokslide? How many of you go by primer condition to gauge pressures?

 

[greyghostnw]

Those primers look far from flat from my house and mine usually look flattish… im 2 tenths in a node below my max…In my pressure testing the case base will have raised plunger marks that first show initial pressure therefore becoming trash as you will never be able to size brass back properly in that state again with headspace gauge and caliper because your reading the raised area and will think your fls die needs adjusting but you never should once your brass has fully expanded in firings.

 

[49ereric]

What he said ^

 

[rickyw]

Yeah those look pretty good

 

[mtnbound]

So... how reliable is reading primers as a sign of pressure? I keep reading on here about "flat" primers being a sign of higher pressure, yet other sources I've read indicate that primer condition has no correlation to pressure signs, flattened primers are more of an indication of chamber dimensions (I may be mis remembering this part). Case in point... I loaded 5 rounds of .243 with the 95gr BT starting at 40gr up to 44gr of Accurate 3100. All 5 cases primer condition was identical... flattened. Bolt lift and extraction on all 5 was easy and smooth, but the 44gr load looked like it had a very slight ejector swipes. What says Rokslide? How many of you go by primer condition to gauge pressures?View attachment 975735

I never rely on just one indicator of possible pressure, and those primers look ok to me.

 

[Backcast88]

I would say those 5 primers are pretty far from flat. When the primer no longer had a rounded edge, that would be flat in my book. This is what I would consider a “flat” primer.

This rifle also had heavy bolt lift but no ejector marker or primer crater. But it’s clearly too hot for this rifle. It was notated in the load book for that rifle and will not be replicated.

As other have said, you can't rely on just 1 indicator of pressure. Your rifle will give you multiple clues of pressure, you just need to be aware what they are for that rifle and adjust accordingly.

For example, it looks like nearly all of those primers have a crater. This can be a sign of pressure. But in this rifle, it just might be one of its quirks. I had a Tikka that would crater primers on just about any load I had. But as powder increased, the warning signs were easy to spot and adjust for to stay below any problems.

 

[5MilesBack]

Pressure signs......blew the primers right out of the brass. UM load. Your primers look totally normal.

 

[Colorado Cowboy]

I have been reloading for 65 years and I have seen my share of flattened primers.
First of all if they are caused by chamber dimensions, then every expended primer will be flat.
Second, flattened primers are just one indicator of excess pressure. Usually the bolt will be harder to lift and the case sometimes will look like its been scratched in the rim where the writing is. It could also show signs of carbon deposits. The primer could also show some metal extruded around where the firing pin hit.

Usually I take the flat primer as a warning first sign of pressure. (Like the yellow light before a traffic signal turns to red). Then I recheck everything, especially the powder charger. A couple of times I have neglected to do this and I have totally blown a primer.....now that gets your attention!!!

 

[JGRaider]

I have been reloading for 65 years and I have seen my share of flattened primers.
First of all if they are caused by chamber dimensions, then every expended primer will be flat.
Second, flattened primers are just one indicator of excess pressure. Usually the bolt will be harder to lift and the case sometimes will look like its been scratched in the rim where the writing is. It could also show signs of carbon deposits. The primer could also show some metal extruded around where the firing pin hit.

Usually I take the flat primer as a warning first sign of pressure. (Like the yellow light before a traffic signal turns to red). Then I recheck everything, especially the powder charger. A couple of times I have neglected to do this and I have totally blown a primer.....now that gets your attention!!!

This.......and get a chronograph, which is the very best indication of pressure.