Pressure sign diagnosis

eLightfoot

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What do you guys look for when choosing a max load. It seems like there is a few different schools of thought. Do you look for:
A. Flattened primer
B. Cratered primer
C. Ejector mark
D. Extractor swipe
E. Sticky bolt

I know that all of these are indications of excessive pressure but what do you guys look for first as a stopping point.
 

hamilton1223

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I would think any 1 of the above generally is a good indicator of a max load and no reason to load past any of those. I mean if I had a sticky bolt, I wouldn't keep loading until I had ejector marks. Or vise versa. A little bit of a flattened primer doesn't seem to bother me but once I start seeing ejector marks, swipes, heavy bolt lift that usually tells me that is enough.
 

HuntHarder

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one of my loads has flattened primers with slight ejector marks. Bolt light is fine and the load is accurate, so that was my final load.
 
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eLightfoot

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In my experience a sticky bolt is definitely way too much pressure. I always stop at seeing a round ejector mark and try to back off a little from there. But just looking for more of a scientific approach to what each of these signs mean and what are acceptable.
 

TauPhi111

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I agree that sticky bolt, cratered primers, and ejector marks and swipes are definite signs of a max load. I'd stop if I hit any one of those. When looking at primers, I feel there are degrees of primer flattening. If there is still some roundness to the edge of the primer, that is generally OK in my experience. If it is so flattened that the edge is almost indistinguishable from the rest of the case head, that is not ok. I also always run my development loads through a chronograph and correlate the speed I am getting with signs I see. I know that if I am starting to see questionable signs of pressure and I am also getting near the max velocity I'd expect, it is probably a good idea to call that the max load.
 

LaHunter

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I would think any 1 of the above generally is a good indicator of a max load and no reason to load past any of those. I mean if I had a sticky bolt, I wouldn't keep loading until I had ejector marks. Or vise versa. A little bit of a flattened primer doesn't seem to bother me but once I start seeing ejector marks, swipes, heavy bolt lift that usually tells me that is enough.
I agree with above post. 'Flattened' primers is subjective. Every single Federal factory round I have ever shot resulted in a primer that appears somewhat flat. Federal primers seem to be a bit softer than others. When I started reloading, I always compared my primers with spent factory rounds that I had.
 

16Bore

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Factory rounds are going to have a lot of slop compared cases sized for a particular chamber. Don’t let it fool ya.
 

Newtosavage

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What do you guys look for when choosing a max load. It seems like there is a few different schools of thought. Do you look for:
A. Flattened primer
B. Cratered primer
C. Ejector mark
D. Extractor swipe
E. Sticky bolt

I know that all of these are indications of excessive pressure but what do you guys look for first as a stopping point.
All except D. Personally, I look at the primer first. Are the shoulders flattening out and is the primer mark starting to crater? Some firing pins will cause primers to look cratered even with mild loads, so you need to know that about your rifle. With my Howa Alpine, I've noticed that the sticky bolt starts to show up before either the primer starts to flatten, or the cratering shows up. So it can be unique to each rifle.
 

Newtosavage

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I agree that sticky bolt, cratered primers, and ejector marks and swipes are definite signs of a max load. I'd stop if I hit any one of those. When looking at primers, I feel there are degrees of primer flattening. If there is still some roundness to the edge of the primer, that is generally OK in my experience. If it is so flattened that the edge is almost indistinguishable from the rest of the case head, that is not ok. I also always run my development loads through a chronograph and correlate the speed I am getting with signs I see. I know that if I am starting to see questionable signs of pressure and I am also getting near the max velocity I'd expect, it is probably a good idea to call that the max load.
Good advice there
 
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eLightfoot

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wyosam

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I generally stop before any of those, when I find a good node around the velocity I want. If I want velocity that is going to be pushing the pressure limits of that cartridge, I pick a different cartridge.


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Hill Difficulty

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What I should do and what I actually do are not always the same.

Some thoughts based on 700 bolt face/extractor design: [Supposing different bolt design feedback will vary.]

While shooting through a series of charges yesterday I realized that my habit is to grab the fired round and look immediately for a dark soot mark anywhere on the outer primer rim and whether there's a plunger dent on the case head.

A tighter bolt lift will always show something on a case head or around the primer, while a case head mark does not always mean a tighter bolt lift.

Not always sure what to think of a primer crater cuz I don't see them often and I don't see them occur when other pressure signs are evident.

A flattened primer depends somewhat on the unfired primer bevel or metal material. Some just appear or seem to go flat no matter what.
 
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maj

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Thanks for posting that video-- made clear a few things I was wondering about.
 

carter33

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I recently worked up a load that I couldn’t find much in the way of solid info on. Specifically a 6.5 PRC shooting a 143 eldx with N565. First signs of pressure were ejector marks/swipes. Those were inconsistent though. They showed up at 58.0 grains on 1-2 rounds and on 59.2 did not show up on at least 1. Bolt lift stickiness seemed to be the most consistent sign which started to show up at 58.5 and was noticeable at all rounds 58.7 up to 59.2.
 

wind gypsy

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There are too many variables to stick with single signs universally.
  1. Some case heads are softer than others and show ejector marks very easily, some don't show signs when way over SAAMI pressure.
  2. Some primers are softer than others and flatten easily, some small primers are pretty darn hard
  3. Some bolt faces have more space around firing pin which allows primers to crater easily
  4. You can get sticky extraction from case web expansion over 2-3 firings with dies that don't size down to the base of the case.

Velocity is a pretty universal measure. That said, I don't absolutely trust reloading manuals on what max velocity should be especially with uncommon chamberings. I have a 26" 6.5x47 that shoots fantastic at 2950 fps with 130s. It doesn't show any pressure on the case or primer but common sense and knowledge about that velocity/bullet weight/barrel length/powder combination tells me it isn't running at mild pressures.
 
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wyosam

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There are too many variables to stick with single signs universally.
  1. Some case heads are softer than others and show ejector marks very easily, some don't show signs when way over SAAMI pressure.
  2. Some primers are softer than others and flatten easily, some small primers are pretty darn hard
  3. Some bolt faces have more space around firing pin which allows primers to crater easily
  4. You can get sticky extraction from case web expansion over 2-3 firings with dies that don't size down to the base of the case.

Velocity is a pretty universal measure. That said, I don't absolutely trust reloading manuals on what max velocity should be especially with uncommon chamberings. That said, I have a 26" 6.5x47 that shoots fantastic at 2950 fps with 130s. It doesn't show any pressure on the case or primer but common sense and knowledge about that velocity/bullet weight/barrel length/powder combination tells me it isn't running at mild pressures.
No, any one sign shouldn’t be taken universally, but they shouldn’t be discounted universally either. If it’s a load without good data to start from, caution seems like a good idea. Forging ahead with multiple pressure signs is not caution. If I’m charging off into the great unknown on a particular load, I would go in with as much of that knowledge as possible. ARE these soft cases that show marks easily (easy enough to test with a load that does have known data)? Are these soft primers that flatten easily? Is this brass in this rifle prone to early sticky bolt lift?


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