Primer pressure signs

Tris88

Well-Known Member
I’m about to change over bullets and start developing a load on some fox bullets I’ve purchased from Ed at Edinburgh Rifles.

I was just looking at some of my last fired rounds from the ELD-x 143gr I have been using. I’m running 34gr of N150 (I know it’s not ideal, it was recommended to me when starting out) with SRP. To me it looks like I’m getting a fair bit of flattening on the primers.

I’ve had some great advice on reloading from here previously and would welcome some more regarding this.

Is this showing high pressure to the point that I need to come down on powder? I’m hoping the next load development will be staying out once I get it right so I want to make sure it’s spot on.
 

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Dalua

Well-Known Member
A few non-expert comments, from a non-expert reloader.
1. You should in any case restart your load development from the book-minimum charge for the new bullets (though you probably knew that)
2. Primers are not a particularly reliable indicator of the absence of high pressure
3. Your primers look OK to me - they'll always flatten somewhat with decent loads, but these have some radius left on the edges. However, see 2. above; in addition to which I've no idea where your load fits in to the scale of recommended charges for that bullet.

In summary, by view of pressure-divination by fired primer appearance is that decent-looking primers (as I'd call yours) are not necessarily and indicator of the absence of high-pressure, but primers that look as though they've been smeared in with a butter-knife probably are an indicator of high-pressure.

I'd be interested to know what others think.
 

Border

Well-Known Member
In the absence of any of the usual signs like stiff bolt lift, bolt head smearing/shiny marks on case head/brass flow into ejector/ flattened primers.
I would develop a load up to max (working up) and when you have determined your max load, load the same piece of brass with the same load 4-5 times and see if the primer pockets are tight or whether they have expanded.
If they have expanded then you are loading too hot and need to back off.
Be aware that higher temperatures for loads developed in colder months can also take you over the redline if you have loaded too hot.
 

Foxyboy43

Well-Known Member
Yep - with Muir i.e. Nope (Wot?).
If you must judge pressure solely by primers (why?) look at extracted ones from the side - is there a clear lip on the bolt-facing side? Then try picking a new inverted primer up with the fired case primer pocket. If the primer can be only just picked up i.e. no major inroads to the pocket that is your first sign, if it slips into the entire pocket then discard any similar cases, pull any remaining cartridges you have and start over again - from the recommended minimum in the most appropriate powder. Not sure which chambering you are using but this applies to all regardless of times reloaded.
good luck.
🦊🦊
 

Laurie

Well-Known Member
Picked this up from a recent range shoot

Kept it as I thought it showed an example of an over pressure effect on a primer

6.5 creed - owner probably chasing velocity

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I wouldn't regard those as necessarily showing over-pressure, in fact most likely not showing that at all. That's a fairly extreme example of extrusion around the firing pin tip caused by an oversize bolt-face hole and/or poor pin to hole fit. The bolt needs a bushing job. Better and cheaper though would be to replace the small primer Peterson brass with large primer from the same outfit, or lapua, or Norma. I used to have a Savage LRP in 204 Ruger that produced near identical extrusions with factory 32 and 39gn VMax ammo despite the rifle having a huge long throat with loads of bullet jump to the lands.

To identify an over-pressure load, look on the bolt face for case-head extrusion back into the ejector button recess and / or brass smearing from it as the bolt was opened.

That aside, as @caberslash says it is a very rich or careless shooter who throws Peterson 6.5CM brass away.
 

Laurie

Well-Known Member
Fired primer condition / appearance can act as a pointer to pressure levels, but as others have said it's not always a consistent nor reliable method. If this is so to some extent with large primers, small primer appearance is much less reliable.

Small Rifle Primer Performance Pt 3 by Laurie Holland

This is the final (results) part of a small primer test series I did a few years ago in SRP Lapua Palma 308 Win brass. Scroll down the piece to a section near the end with five primers fired side by side for group size without the MagnetoSpeed chronograph attached and to ascertain primer appearance. There are two pics - one straight on and one angled to see the fired cup radius. There are considerable appearance differences between the five despite the same load being used across all rounds and pressures being within a small range, changing only by primer model performance. In fact, one Russian PMC model (Murom nowadays) 'blanked' despite the Stolle action having a small diameter pin and pretty good bolt fit.
 

Tris88

Well-Known Member
That’s great info thanks everyone. I’ll look at changing brass at some point. I have got about 700 SRP left and over 100 cases that are still going strong, so I won’t be throwing those away yet.
 

Sagebrush

Well-Known Member
Your primers look rounded on the edges from this side of the big water. So like the other gentlemen stated; Nope Sir.
 

Edinburgh Rifles

Well-Known Member
Picked this up from a recent range shoot

Kept it as I thought it showed an example of an over pressure effect on a primer

6.5 creed - owner probably chasing velocity

View attachment 208835

View attachment 208833
That appear to be a GGG stamped 308 case
Aside from that it’s displaying physical issues with rifle not necessarily ammo

OP
Your primers look fine
What is the load data and OAL and I will run it through QL to get a projected pressure?
 

25 Sharps

Well-Known Member
That appear to be a GGG stamped 308 case
Aside from that it’s displaying physical issues with rifle not necessarily ammo

OP
Your primers look fine
What is the load data and OAL and I will run it through QL to get a projected pressure?

It does, could have been necked down and trimmed to form creedmoor brass maybe?

GGG forms into creedmoor really nicely but the necks need turning to the appropriate wall thickness
 
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