Pressure signs?

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Pressure signs?

Post by Rod_outbak » 28 Oct 2018, 9:33 pm

Folks,

Attached is the .308 brass I currently have loaded with 125Gn Hornady SST projectiles. I think this would be the third loading (including original factory)

I'm pretty happy with their performance, but I thought I should ask if the brass looks about right for pressure signs?

Load is 49Gns of AR2208, which is half-way up the recommended range.
I havent chrono'ed them yet, but they would have to be departing somewhere just over 3000fps (20" barrel in a RPR)

I see there is the occasional slight cratering, but the primers arent excessively flattened.
In my mind, I see them as warm, but not hot loads. And they hit hard

What do you think?
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Re: Pressure signs?

Post by Apollo » 28 Oct 2018, 10:26 pm

Why do you ask about pressure signs..?? What has lead to this question.

You show a photo of the head end of cases with fired primers which look fine but perhaps the primer is slightly flattened. What you should show is an unfired against a fired case BUT that still shows very little about pressure.

The worst indicator of pressure is looking at the primer. What primer, soft or hard, thick or thin , brand of primer all look different and hence looking at a fired case primer is no indication of pressure. The firing pin crater or lack there of is also no indication of pressure but more so a combination of primer type/hardness/thickness and/or firing pin clearance in the bolt face.

One big indicator of pressure is the measurement of an unfired case around the web area diameter compared to that of a fired case plus other case measurements but not what they look like. Don't be led by the misinformation that primers show pressure signs, they do not...!!! Example is a Federal Primer which is super soft and thin to a CCI which is harder and thicker hence shows no change from when it wasn't even fired other than the firing pin strike.

I don't own a 308 so I'm not familiar with the calibre but I do play with much higher pressure calibre cartridges like the 6.5x47L, .204 Ruger and they are something you don't put soft Federal Primers in or you will not only end up with a very flat primer, firing pin crater but more so a punched primer and wear the gas blast back past the bolt....just the wrong primer.
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Re: Pressure signs?

Post by Apollo » 28 Oct 2018, 10:39 pm

Sorry, these are Large Rifle Primers....so most all brands I have measurements from show the same case thickness. I'm use to playing with Small Primers.

The only large I use would be my .243W where I switched from Federal (which were soft and flattened) to CCI which didn't look any different after being fired then to CCI Benchrest for there more consistant results...sorry, off track and different topic.
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Re: Pressure signs?

Post by Rod_outbak » 28 Oct 2018, 10:40 pm

Gees, mate!
Thanks so much for the patronizing lecture.

I asked dared ask a question to learn; funnily enough.

Thanks for encouraging me to not bother asking in future.
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Re: Pressure signs?

Post by Apollo » 28 Oct 2018, 10:52 pm

Wow, lecture. It wasn't...!!! Ask a question to learn, it wasn't but more like whats wrong with my load...

I wasn't expecting that response...

You asked a question about "Pressure". I gave you advice on pressure signs BUT Primers aren't one of them.

It's plain you know more than my 50 years of experience so I won't bother again either.
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Re: Pressure signs?

Post by Member-Deleted » 28 Oct 2018, 11:55 pm

G'day Rod, Am I right to go mate ?
Okay then mate i'm no professor on the subject but I did learn a fair bit from some of the boys up here awhile back
I run an Ackley 22-250 as well as my 7mm and sako 22-250
When I was working out loads I was told to watch the primer and know what primer I was using ie hard-soft
Flattening isn't always high pressure signs soft will flattern more than the hard as you probably know
What I did find was a slight leakage from around the primer after being shot but on a new brass or only once or twice fired ones
with tight primer pockets the reason for new or near new brass as it's easy to get leakage around the primers if the brass is old and has slightly enlarged primer pockets especially when the pressure is reasonably high usually I got cratering around the pin indent on the primer as well if the primer
socket was a little loose
I've seen cratering caused by head spacing not being good but mine was from loose pockets
Those primers of yours look a little flat but the primers of my factory loads on the 22-250 go flatter than that unless your getting leakage past the primers or from the neck back along the shell for me it would be ok but if they got overly flat then i'd be careful and check on a few books
Blow back along the brass neck can also be caused by wrongly trimming the brass
When I got leakage past the primer i'd drop the powder back in 1gr increments til it stopped then back another 2gr that always fixed it
and that would be the max load for me
Hope this helps but it is only what I've been told , tried and tested but there would be other ways of doing things to find out high pressure signs
Hard to tell with the pic of your brass but as I said above going on the primer i'd stick with it unless problems start to appear :thumbsup:
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Re: Pressure signs?

Post by bigrich » 29 Oct 2018, 4:40 am

They look fine to me rod. I bin running federal primers in 6.5x55 for a while now and they tend to look like yours after firing. I’m under maximum load but everything seems fine in my situation. Just the federal are soft primers, but they work well. You could switch to CCI which are a harder cup I’m told :thumbsup:
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Re: Pressure signs?

Post by straightshooter » 29 Oct 2018, 7:20 am

Rod_outbak wrote:Folks,

Attached is the .308 brass I currently have loaded with 125Gn Hornady SST projectiles. I think this would be the third loading (including original factory)

I'm pretty happy with their performance, but I thought I should ask if the brass looks about right for pressure signs?

Load is 49Gns of AR2208, which is half-way up the recommended range.
I havent chrono'ed them yet, but they would have to be departing somewhere just over 3000fps (20" barrel in a RPR)

I see there is the occasional slight cratering, but the primers arent excessively flattened.
In my mind, I see them as warm, but not hot loads. And they hit hard

What do you think?

From the picture there is nothing OBVIOUS to see within the picture that is wrong.
Unless there are obvious destructive signs such as extrusion into extractor slot then the only way somebody without access to a pressure testing laboratory can get any idea of whether the operating pressure of a cartridge is exceeding safe limits is via comparative before and after measurements of web expansion of your cases.
To do this with any semblance of accuracy you need a quality blade micrometer with resolution of no less than 0.0001 thou and make multiple measurements in the clean extractor groove before and after firing and compare the averages of those before and after measurements.
Trying to make this kind of measurement, and expecting a meaningful result, with a low resolution instrument such as digital or dial calipers is delusional.
The best advice to follow is to never exceed the exact recipes published by reputable sources such as powder or bullet makers.
Sadly that does not include (in decreasing order of credibility) gun writers, shooting acquaintances, bloggers and anonymous forum posters.
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Re: Pressure signs?

Post by marksman » 29 Oct 2018, 10:49 am

I think they look fine :thumbsup:
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Re: Pressure signs?

Post by SCJ429 » 29 Oct 2018, 6:27 pm

They look fine to me also unless you had to hammer the bolt open. Also pierced or blown primers can also indicate you have exceeded the design limits of that primer. It is good to watch your primers to see how pressure is modifying the fired primer. Loose primer pockets are also a good sign your loads are fairly warm. Apollo offered some sound advice and I am sure he didn't mean it to come across as a lecture.
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Re: Pressure signs?

Post by Member-Deleted » 04 Nov 2018, 3:16 pm

follow up questions re signs:
what if anything does it mean if the head of the case has signs of rubbing/wear... this is once fired factory OSA 308 out of a new Howa (less than 40 rounds).

also, had one reload (223 on its first reload/2nd firing) refuse to chamber. could not close the bolt on it. to the naked eye appears identical to every other one in that batch.
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Re: Pressure signs?

Post by bigrich » 04 Nov 2018, 6:48 pm

Member-Deleted wrote:follow up questions re signs:
what if anything does it mean if the head of the case has signs of rubbing/wear... this is once fired factory OSA 308 out of a new Howa (less than 40 rounds).

also, had one reload (223 on its first reload/2nd firing) refuse to chamber. could not close the bolt on it. to the naked eye appears identical to every other one in that batch.


how do you mean rubbing or wear ? can you post a pic ? :thumbsup:
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Re: Pressure signs?

Post by Wm.Traynor » 04 Nov 2018, 6:53 pm

In the case (NPI), of the 308 I'm guessing you mean either the base where the headstamp is or the walls at the web surrounding the primer pocket.
How is the extraction?
Ordinarily I would say that I don't like rub marks in either location. Can you do pics?
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Re: Pressure signs?

Post by Homer » 04 Nov 2018, 7:07 pm

G'Day Fella's,

Rod_outbak, it's always difficult to make assumption, regarding your question, on excessive pressure.
It is always a Smart thing, to ask a Dumb Question first, rather than make a Dumb Mistake!
From what I can see, I would say these primers are right up there, as far as their pressure indicators go.

From what I understand, the OSA .308 Win cases are ADI Military cases, with an OSA head stamp?
If this is correct, military cartridge cases, generally weigh more than sporting cases, and if this is the case with these OSA cases, that would help to explain why you have flattened primers, with out reaching the Recommended Maximum powder charge.
What I'm saying is, the outside dimensions have to be the same, so they will fit in all rifles, chambered for that cartridge.
Because of the potential extreme conditions and situations, military people can find themselves in, they manufacture the cases to have a smaller inside capacity (and consequently, thicker case walls to the rear of the case) than normal sporting cartridge cases, to cope with these same extreme situations. This reduces internal case capacity, and up's pressure sooner, when you do a ladder test, compared to when sporting type manufactured cases, of the same chambering are used.
FYI, I have an old batch of Wincester brand sporting .308 Win cases, and these weigh only 162 grns, when deprimed.

The question I would like to ask you is, what brand of primers are they, in the above photo?

Hope that helps

D'oh!
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Last edited by Homer on 04 Nov 2018, 7:21 pm, edited 2 times in total.
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Re: Pressure signs?

Post by Apollo » 04 Nov 2018, 7:15 pm

Not exactly sure of where this is heading trying to read the last couple of posts. If they are quotes or questions.

If we are still on pressure signs and you are looking at a highly polished cartridge case before and then after firing. If you see a rub mark or as I would say a scoured surface on the case down from the shoulder to the case head then you are experiencing case expansion where it shouldn't be and hence something to have a very long hard think about. Measurements are the best way to keep track from a new unfired case to what happens after the first firing then subsequent firing. A thou or so first then nothing should be the norm but if it expands more there is a big problem.

A cartridge case should expand on firing then spring back to very near it's initial size afterwards and on extraction should really not leave any mark at all on the cartridge case. If it does is one possible sign or over pressure where the case has been over expanded past it's limit of return. Hard to explain. Then on extraction it will show marks on the case body where it's gone past it's limit of no return and end up looking like a scrape mark as it's withdrawn.

Probably at the same time you may see ejector marks on the case head and a swipe across the case head from the tight bolt movement. They are excessive pressure signs yet alone a difference in bolt lift.

Marks on the case head and flat fired primers can also be found from incorrect case sizing by bumping back a shoulder to far creating excessive head space.

EDIT... Two more posts before I submitted my reply... Sorry
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Re: Pressure signs?

Post by Member-Deleted » 04 Nov 2018, 8:18 pm

Rod, sorry about the thread hijack but i read your original post and you asked the questions i've also been wondering about.

Bigrich, WM.Traynor and Apollo, will post photos of cases tomorrow from work. it's probably nothing but ive never seen it before

.
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Re: Pressure signs?

Post by Member-Deleted » 04 Nov 2018, 8:19 pm

Rod, sorry about the thread hijack but i read your original post and you asked the questions i've also been wondering about.

Bigrich, WM.Traynor and Apollo, will post photos of cases tomorrow from work. it's probably nothing but ive never seen it before

.
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Re: Pressure signs?

Post by Member-Deleted » 05 Nov 2018, 9:09 am

IMG_0342 (002).jpg
IMG_0342 (002).jpg (24.06 KiB) Viewed 6825 times
the OSA cases showing "rubbing", the Hornady clear by comparison. Both are once fired factory loads [the OSA is reportedly 3000fps at the muzzle]
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Re: Pressure signs?

Post by Member-Deleted » 05 Nov 2018, 9:46 am

and another
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Re: Pressure signs?

Post by Apollo » 05 Nov 2018, 11:25 am

The first thing I would do if I saw that mark on the head of a case (OSA) and not on the Hornady would be to measure the case length. Shoulder datum point to case head (base). Wonder if the OSA show a little bolt closure resistance.

I have seen that on my own cases of different calibres and it is a case that is a touch long that needs the shoulder bumped a touch. Being new it might just be they are a touch long for your chamber, just a guess as I don't know what chamber you have (make of rifle) and it's dimensions. In my case I know that a couple of my chambers which are custom chambering were done as a "crush fit" so there is bolt resistance on closure.

The swipe mark is the bolt face closing then opening on a tight case. There is no sign of an ejector mark on the case head that I can see.
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Re: Pressure signs?

Post by Member-Deleted » 05 Nov 2018, 12:41 pm

Apollo,
thanks for that, i'll do some measuring of case length. It's a Howa. Now that you mention it, I did have one OSA round [not necessarily the cases in the photos] resist closure. i extracted it and examined it, worked the bolt empty a few times to check it was still operating properly then reloaded it and closed the bolt with a little bit more effort. it only happened with the one round, the rest seemed to cycle normally.
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Re: Pressure signs?

Post by Apollo » 05 Nov 2018, 1:40 pm

I don't know if you do already but I would be putting a tad of high pressure grease on your bolt lug faces to reduce any bolt lug galling that might happen when using this OSA ammo. As we do in competition shooting, the lugs are greased before every detail. In my case about every 8 rounds.

Most all my competition ammo is pretty close to maximum length, say with a touch over 0.001" headspace and that is about all I ever bump shoulders back if they get tight. On varminting/hunting ammo it's normally about 0.002" headspace I set my either FLS or Bump Dies at if needed but the majority of my calibres don't grow so very seldom do they need shoulders bumped back.
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Re: Pressure signs?

Post by bigrich » 05 Nov 2018, 8:48 pm

maybe case length is a bit long for your chamber ? i've had a similar thing where i was useing some fed 130 gn hp in my 308 sako. felt tight to close, slight rub marks, not as obvious as yours. when i went to reload, these cases were over max length by a couple of thou. if you think that's odd some fed 222 factory ammo brass was 30 thou shorter than spec after firing ! dunno if i'll buy any more fed ammo...... :unknown:
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Re: Pressure signs?

Post by RoginaJack » 19 Nov 2018, 9:12 pm

Hi Apollo, here is a informative article on reloading and using the primer as a pressure test.

I think the primer is one of the first to show "Bolt Thrust" or Breech Pressure" signs. Many years ago when I 1st started reloading, I was told that the primer/cartridge base would be the first to show signs of pressure.

https://www.youtube.com/watch?time_cont ... APC4xixPtY
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Re: Pressure signs?

Post by Sergeant Hartman » 19 Nov 2018, 10:17 pm

And today I just read how a guy was running 43gr of 2208 with 95gr proj in a 243w. Why don't ppl look at manuals or basic couple of videos before reloading.
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Re: Pressure signs?

Post by bigrich » 20 Nov 2018, 4:48 am

Ziad wrote:And today I just read how a guy was running 43gr of 2208 with 95gr proj in a 243w. Why don't ppl look at manuals or basic couple of videos before reloading.


That fella’s name wasn’t Wyle E Coyote was it ? Rifle and ammo come in a Acme crate ? :lol: ya just gotta wonder about some people’s common sense and intelligence
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Re: Pressure signs?

Post by Sergeant Hartman » 20 Nov 2018, 7:07 am

And he was complaining why his reloaded ammo was cratering primers. He got the gun from a friend and some reloaded ammo, and the friend told him it was 43gr. Obviously someone made a mistake (or wanted to kill the guy) butthe guy sounds have atleast checked
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Re: Pressure signs?

Post by TassieTiger » 20 Nov 2018, 7:24 am

Some people do not have the right attitude for reloading...true story.
I’ve watched a guy - literally set his hornady elec scales, plugs in his target number and then goes off and primes / resizes until he hears the “over” alarm.
I said to him, your not going to use that load are you?
Ready for this...”yeah - when it says over, it means it’s finished dispensing, it’s dispensing cycle is now “over” and you can take the powder off the scale.
Wtf. Wtf. Wtf.
When I explained to him that “over” was an alarm that the dispensary had gone over his target, he struggled to believe me...”worked for me for years...” he said.
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