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The Shadow (Super Mod)
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Discussion Starter #1 (Edited)
This will be long-winded, I'm sure. But is meant ONLY to point out some honest realities about what we think we "know", and how much we really don't when it comes to reloading. After a recent miserably failed thread, I think this may be warranted.

What do we know?
Brass alloy? - Not publicly published, as mainstream standards.
Tensile strength? - Not publicly published, that I know of.
Nomimal variance allowed in case production? - Not publicly published.
Brass cases AND primers are a very very poor indicator of ACTUAL pressures. Better than praying over chicken bones, but not much better than that.
Powder nominal variances? - VERY few published.
Lot numbers tested in public data? - NO.
Who makes our powders? - Not unless you read MZ5's post, AND can stay ahead of supplier swaps.
Powders that DO list variances, and EVERY bottle of powder I've ever seen on the shelves in the past several decades have a warning. They tell you that lots CAN vary by 10%.
We also know that powders continually lose moisture content from Sealed containers, changing the burning rates. We know that no one in the industry(on any large scale) loads powder by weight, that's a reloader thing.
Lots of unknowns there...

If some bozo on the interwebs, or in a gun-rag expounds that XX.X grains of this powder will give you
certain results in your 308-super-ninja-2000, and not be over-pressure. Should you REALLY take his advice as gospel? Not if you care about yourself, those around you, or your equipment.

Lets look at some examples from my copies of the following:
Nosler #6 manual(NB), Nosler online(NO), Hornady #9(H), Current Hodgdon online reloading webpage(HO).
308 Winchester, firing 175gr bullets, with IMR-4895. Max's listed.

NB - 43gr @ 2708fps
NO - 41.5gr @ 2559fps
H - 41.1gr @ 2400 fps
HO - 45gr @ 2704fps

Are some "Lawyered"? There is ZERO basis to make that leap of faith. Re-read what we don't know, what isn't listed about what was tested, and you are left with REASONALBY normal variation in coponents tested, for an unlisted date tested.

Ah, but you say there is a difference in the jackets. Some are super-swinging-sexy-awesomeness, and that's the difference! Is it?? Well, here are some test results, in ALL examples the jump to lands is the same distance, the powder charge is the same, the rifle is the same, only the sexyness of the bullets is different. Powder charge in the 175 however is different, to illustrate a point I'll get to in a moment.






Ignore that some of the traces look noisey. The point is the Average Pressures, and the Velocities. All the same velocity AND pressure. The difference in the 175gr obviously charge, BUT it also has a different lot of that powder. Another reason to not just ASSume you can automatically push lighter bullets faster than heavier at the same pressure. It depends on the powder and multitude of variables.

You think your barrel is "Faster" than another?? Great! Show me the pressure tested proof, I would love to see it! Chrono data without Pressure testing is meaningless. Brass and primers DO NOT accurately report pressure, period, end of story.


Some powders when used in the correct application, have a progressive burning curve; meaning they speed-up or slow-down with pressures. Here is a perfect example in the Creedmoor. The ONLY difference is in the charge amount.




Notice the shape is different, almost a plateau on one of them. Due to that more efficient "Push" you significantly drop the operating pressure, but not significantly drop velocity. The chrono alone does not tell you what is actually happening in that firing event.

Another example of why a chrony alone isn't safe:


That is boardering on a blow-up, but the chronograph would say "party-on, Garth!". That load is dead in the middle of a load manual, but the bullet construction was swapped.


So what about primers? They make a difference right? Well, they certainly can. You CAN also have a particular application where they do not, see below.





Can you swap bullets with no change? Sometimes yes, somethimes no. Both example shown above. Can you Swap primers with no change? Sometimes yes, sometimes no.
So the points I hope I made in all this, is that unless you CAN accurately and repeatedly measure these things, then you don't know what is actually going on. If you don't know, then ALWAYS remember the following basic rules of reloading:

Stop whenever you reach either of the following:
Reached published max charge.
OR
Reached published max velocity.

IF you change something, then start your load process over. If the pain of getting off the couch to go ourdoors and shoot is burdensome, or you consider any part of it a "waste"; you need to find a different hobby, this isn't paint by numbers. Enjoying the outdoors, and LEARNING is a large part of this deal. I understand that not everyone can go out their backdoor and shoot. Again, if it is too burdensome to go shooting, then even if you weren't trying to learn reloading, you likely wouldn't shoot enough to learn the marksmanship part well either.
It's not a judgement, just a matter of reality for your particular situation.
 

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Thanks for your time and trouble explaining this. I do try to make safe loads and have experienced the problems of swapping bullets of the same weight but different construction and design by the same manufacture so I never interchange bullets of the same weight no matter who says it can be done.
 

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Even though I possess a limited degree of intellect regarding internal ballistics, I do find this very informative. I often study various pressure curves, I feel they provide me with some perspective regarding bullets and powders, and how they effect load development. I am not the type that relies on chrony results as the final decisive data function, not me. I focus on the whole picture, in that there are various other effects, that even without the trace evidence, which I can't afford on my meager budget, that can still provide at least some useful insight.

But I do truly appreciate the time and effort you've invested to provide us with this material. I will be spending some additional time studying this post, just so much to be taken in during a single read, but it's holds great value within this hobby and at least for me, it's well worth the study time. I may not understand all of it, but I do have a fairly good understanding of applied physics and their effects.

Thank you!

SMOA
 

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Elk Whisperer (Super Moderator)
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Darkker, I've made it a sticky so it won't get lost in the clutter.

Very informative thread and as SMOA stated, it will take more than one reading (for this caveman anyway) to get all the goody out of it.

So, where do I get one of these pressure trace thingies and how much is it so I can tell 't missus.

RJ
 

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What exactly do those graphs actually show?

I'm not actually trying to be contrary, I'm just pointing out that without the PRIMER to look at and to judge how close that first, weakest, most visible sign of pressure in YOUR gun is to failing, it's just exercises in numbers which are arbitrary to the key question: How well is MY rifle containing the gas I feed it?

That would be a terrific experiment to run while measuring primer indents and rim gap by microscope to correlate what you're measuring with the condition of that very important weakest link.

The problem is that the same load in different rifles give different pressure indications and it is those indicators and not numbers that we as shooters have to pay close attention to.

"Failure" is defined as gas escaping anywhere but the muzzle.
 

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The strain gauge makes the test uniform. Just need to move the same gauge to a different firearm to maintain that I think.
 

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My point is firearms centric instead of numbers centric, so I apologize for the confusion.

My test was with a Rem Model 700, 7mm Rem Mag that had somehow wedged itself in a set of dual wheels that beat the stock and parts off it and put a gentle bend in the barrel....upwards. I straightened the barrel by beating it on a tire and cut the two inches of battered crown off the end and mounted it in a scrap stock and strapped it to my test tire.

Factory ammo made no smoke, but a flat primer for sure. It was plain the rippled barrel had pushed pressures up. I shot two more rounds and marked the cases. Next day, I ran the chambering reamer in to create a total of .007 HS. It had .002 to start. The same clean bore and chamber and clean factory ammo blew the primer at the firing pin dimple and leaked around the edges some. I shot two more with the same results. Obviously over-pressured with safe ammo that was affected by two different faults.
The third test was with .020 excess headspace and that space occupied by oil based modeling clay. THAT was exciting and damaging and scary and the test was over.
 

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The Shadow (Super Mod)
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Discussion Starter #8 (Edited)
RJ:
https://www.shootingsoftware.com/pressure.htm
Will cost you about the price of an entry level rifle.
But as many who have used them know, can leave you with so many more questions than you thought you had. Truly is for the technically interested. For a standard cartridge with well published(more than one source) date, there is no reason for it.

Jack:
Those graphs are a recording of the actual pressures in the firing event in a Ruger hawkeye with the strain guage sytem attached. Do a quick search for my posts and you'll see the primers in the "run away" graph above. They do not show "signs" of anything remotely out of the ordinary, no funny extraction, report, recoil. No extractor groove stretch. I do also have a post where I did measure the massive expansion on some brass that was running near the 45,000 psi mark. Good ol Federal soft-headed garbage... But the bit about "different signs in different rifles" is exactly my point. "Signs" are at best a very very poor reporter of actual pressures being run. Which is why you should not use them as your yardstick, so to speak.

Cheese:
The system has you attach a different strain guage to each rifle you wish to test. Then you can plug any rifles guage into the computer and test away.
 

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If there are no 'signs' of pressure, there was no pressure on the parts that make a difference. I think what you're seeing is odd combustion that explains 'flyers' and why some powders are not generally used in some calibers.

The actual value of the pressure generated makes no difference at all. If there is too little, the case won't obturate and gas will leak out he back. If there is too much, the primer will fail and squirt gas out the back. BOTH are bad and it is the primer that tells us how bad it is, not how much the chamber swells or how flat a copper pellet mashes.
Those are comparative numbers that may mean something with some actions, but assuming a modern bolt action in good mechanical working order it means very little unless we know where the top is. And it is that 'top' that varies SO much an SO many rifles due to MANY different causes besides powder charge and make of the primer.

I admire somebody that can shoot for data, but I shoot for the holes and my only concern is accuracy and safety. If the primers are good, extraction easy and accuracy good, the chart can say it spikes to 100kpsi three times going down the barrel and that's just fine with me. I assume it always has. Interesting to know but of no practical value unless you shoot for data.

I would love to take one rifle and that program and find out some things, though. The numbers would make no difference but the comparisons would.
 

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The Shadow (Super Mod)
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Discussion Starter #10 (Edited)
1) If there are no 'signs' of pressure, there was no pressure on the parts that make a difference.

2) The actual value of the pressure generated makes no difference at all. If there is too little, the case won't obturate and gas will leak out he back. If there is too much, the primer will fail and squirt gas out the back. BOTH are bad and it is the primer that tells us how bad it is,

3) I admire somebody that can shoot for data, but I shoot for the holes and my only concern is accuracy and safety. If the primers are good, extraction easy and accuracy good, the chart can say it spikes to 100kpsi three times going down the barrel and that's just fine with me. I assume it always has. Interesting to know but of no practical value unless you shoot for data.
Jack, you need to re-read my post and think about this for a mnute.

These are not "charts", these are actual recordings of actual firing events and their actual pressures.

If you honestly care about safety, you will never again say you don't care if pressure spikes to 100K, three times while a bullet is in a barrel.
 

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Sorry, you're still not getting my point. 100kpsi is a FIGURE and not a PRESSURE.

I've NEVER said that primers can 'read' pressure, only that primers tell the observer how much 'pressure' is acting on it.
The primer doesn't 'read' in kpsi, it tells you when its under too much strain and to STOP IT! Where that red-line IS is told by how well the primer is holding up. To confuse it with measuring methods and numbers mean nothing to the gas seal, only to those comparing those readings with something else.

A primer that flattens and puckers can happen at 48kpsi or at 62kpsi. BOTH are telling you the load is over max and to back off. Assign any numbers you like, the pressure is "too high" and that's enough information for the careful handloader/shooter.
For the data collector, it is a point of curiosity to be argued over and theories postulated, but the REALITY remains the same. The load is too hot. The primer told me so.
 

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The Shadow (Super Mod)
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Discussion Starter #12 (Edited)
Sorry, you're still not getting my point. 100kpsi is a FIGURE and not a PRESSURE.

I've NEVER said that primers can 'read' pressure, only that primers tell the observer how much 'pressure' is acting on it.
Your rambling pontifications are circular, generally unsafe, and tiring.

You started off being totally bewildered by a pressure trace, asking what they said, what they mean. To magically trying to tell me how to read them and what they might mean, and what pictures I do or don't need to show you. To some random circular nonsense:
You admire someone shooting for data, but it has no practical usage unless shooting for data.
You don't care about a stain gauge system on a rifle, nor it's accuracy. You had a rifle somehow work its way into a set of duals so you know pressures.
Your primers don't read pressure, only tell someone looking at them an amount of Force exerted upon them.


That is a hot mess of absolutely nothing.

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