Smushed primers, and reloading manuals

Status
Not open for further replies.
Years ago, I started gathering materials for an article on judging pressure by primer flatness. I loaded a batch of cartridges with widely varying charges, marked each primer, fired the cartridges, and then popped the primers out.

Under the microscope, I arranged the primers from least to most flattened. There was no correlation between flatness and powder charge. You can't judge pressure by looking at primers.

Of course, if you have primers falling out, extruding into the firing pin hole, or flowing excessively, those are problems. But short of that, there is so much variation in primer hardness that you can't gauge pressure by primer flatness.


 
Last edited:
denton said:
Years ago, I started gathering materials for an article on judging pressure by primer flatness. I loaded a batch of cartridges with widely varying charges, marked each primer, fired the cartridges, and the popped the primers out.

Under the microscope, I arranged the primers from least to most flattened. There was no correlation between flatness and powder charge. You can't judge pressure by looking at primers.

Of course, if you have primers falling out, extruding into the firing pin hole, or flowing excessively, those are problems. But short of that, there is so much variation in primer hardness that you can't gauge pressure by primer flatness.

Click to expand...
Was this with the same brand of primers or different brands. I concur that compared different brands would be almost impossible, but comparing the same brand "federal in particular" would give good comparative analysis.
 
AJC1 said:
Was this with the same brand of primers or different brands. I concur that compared different brands would be almost impossible, but comparing the same brand "federal in particular" would give good comparative analysis.
Click to expand...

Same brand of primers from the same box.
 
GBExpat said:
Aaaahhhh ... just to impress everyone, throwing around that Technical Terminology again, I see. ;)
Click to expand...
I could have gone with "mushy peas", but you know, really, who in their might mind as a adult would willing load them? /j

Spoke to several folk today, whom I respect for their acumen in our sport/hobby. My concern is taken care of.

Thank you all for your input, even with grey hair there is always more to learn.
 
AJC1 said:
I would be interested to see the test results if they are available... lots of variables to try and control...
Click to expand...

That experiment was 15-20 years ago, and since it didn't produce a result I wanted to publish I did not preserve the data. However, I typically use freshly trimmed brass from the same lot and same number of firings, and I keep a thermocouple on the barrel to regulate temperature. If primers won't tell the tale under those conditions, they certainly won't under typical conditions.
 
denton said:
That experiment was 15-20 years ago, and since it didn't produce a result I wanted to publish I did not preserve the data. However, I typically use freshly trimmed brass from the same lot and same number of firings, and I keep a thermocouple on the barrel to regulate temperature. If primers won't tell the tale under those conditions, they certainly won't under typical conditions.
Click to expand...
Which brand? I use cci and if they show pressure I'm happy to have lived through it...
 
lordpaxman said:
I’d be interested to hear what they respond with, but with regards to your primer pictures I don’t see anything wrong with them. I’m not sure there’s a place on this forum with what a truly flattened primer looks like, but essentially it’ll flow completely into the primer pocket even with head brass. You may even see a pierced primer or it’ll loosen entirely and fall out of the pocket. That’s the no go zone.
Your Hornady manual most likely lists loads for their bullet, not the Sierra. There may be small differences in the technology used and therefore could account for some of their differences in charges. It’s not unusual to see that, or COL differences accounting for it.
Did you first find out what Max and Working COL you need? Love the avatar….
Click to expand...
 

Attachments

  • IMG_20191212_111311544.jpg
    IMG_20191212_111311544.jpg
    56.5 KB · Views: 24
amp-rat said:
I could have gone with "mushy peas", but you know, really, who in their might mind as a adult would willing load them? /j

Spoke to several folk today, whom I respect for their acumen in our sport/hobby. My concern is taken care of.

Thank you all for your input, even with grey hair there is always more to learn.
Click to expand...
Aw, c’mon man! All we are saying is, give whirled peas a chance.
 
Received a very good response from Sierra;
"We will always recommend using the data provided by the bullet manufacturer of the projectiles in use. Since we haven’t developed data for the A4064, your best option then turns to the powder manufacturer but you have found the exception to this rule. Your pressure signs prove your point to stop early but there is one more thing I’ll point out. When it comes to comparing the two different brands of 4064, IMR and Accurate, they compare at a grain or so in our pressure data. What I mean by that is that we have shot several cartridges in our current #6 manual that put them side by side in the same case using the same primer pushing the same bullet. The same velocities were produced within a grain or so of each other and that carries over to the top ends that can vary slightly in charge and velocity. In my opinion, the Hornady data you show looks more realistic and the IMR version is a little hotter burning."

Great data point!
 
amp-rat said:
Received a very good response from Sierra;
"We will always recommend using the data provided by the bullet manufacturer of the projectiles in use. Since we haven’t developed data for the A4064, your best option then turns to the powder manufacturer but you have found the exception to this rule. Your pressure signs prove your point to stop early but there is one more thing I’ll point out. When it comes to comparing the two different brands of 4064, IMR and Accurate, they compare at a grain or so in our pressure data. What I mean by that is that we have shot several cartridges in our current #6 manual that put them side by side in the same case using the same primer pushing the same bullet. The same velocities were produced within a grain or so of each other and that carries over to the top ends that can vary slightly in charge and velocity. In my opinion, the Hornady data you show looks more realistic and the IMR version is a little hotter burning."

Great data point!
Click to expand...
That was a great response until the last line. Being technically correct is critical. He ment one was faster because I would bet the kingdom they didn't measure flame front temperature. They are both single base with flame fronts much lower than double base powders.
 
AJC1 said:
That was a great response until the last line. Being technically correct is critical. He ment one was faster because I would bet the kingdom they didn't measure flame front temperature. They are both single base with flame fronts much lower than double base powders.
Click to expand...

Then how should it be interpreted?
 
Status
Not open for further replies.

Similar threads

T
  • Locked
M1 Garand reloading primer issue
Replies
9
Views
870
medalguy
M
J
  • Locked
Ruptured Primer
2
Replies
28
Views
2K
243winxb
243winxb
E
  • Locked
Head separations cause flat primers?
Replies
16
Views
623
Nature Boy
Nature Boy
P
  • Locked
Raised Primers
Replies
9
Views
757
Prospero
P
T
  • Locked
Flattened WLP primers
2
Replies
25
Views
1K
Old Dog Man
O
Back
Top