Wildcat ?? Case pressure

[hemiford]

I'm still learning (a lot) here, I hope this isn't a silly question.

SAAMI rates a given cartridge for max pressure. I'm not familiar
with how this max rating is established, but, there it is.

Question, when you build a wildcat on a given cartridge, are you bound
by the same max pressure ?

I know some manufacturer's brass is more robust than others. So , when
you work up new loads, you cannot directly measure your pressures,
you must go by visible deformation signs on the brass.

Does anyone know if you typically end up at a higher pressure than
the SAAMI rating ?

 

[Mikecr]

SAAMI today seems such loose science, and loose standards, that I would not assign any hard credit to it.
Keep in mind also that there are differences between pressure(actual) and pressure problems. Relatively low pressure loading for a BAT actioned .223 could be extreme for a REM actioned .260, and there are many design and reloading factors leading to problems at varying pressures. Then there is viable(for brass life) -vs- safety.
Hence the golden rule: always start low & work up.

For a beginner, a little research for anecdotal results seems more useful than SAAMI listings.

 

[Lefty7mmstw]

SAAMI today seems such loose science, and loose standards, that I would not assign any hard credit to it.
Keep in mind also that there are differences between pressure(actual) and pressure problems. Relatively low pressure loading for a BAT actioned .223 could be extreme for a REM actioned .260, and there are many design and reloading factors leading to problems at varying pressures. Then there is viable(for brass life) -vs- safety.
Hence the golden rule: always start low & work up.

For a beginner, a little research for anecdotal results seems more useful than SAAMI listings.

+1...

the only thing I'll add is to go with a big enough chambering to get the results you want without having to hot rod the snot out of the rifle to get there. If you end up with a bit of a slow barrel you may not get to your expectations otherwise.

 

[MagnumManiac]

The general concensus for wildcat pressures is a misnomer. Example, the 30-06 is loaded, and quoted by SAAMI, at lower pressures than either the 25-06 or 270 Win, even though the brass cases are somewhat identical apart from calibre.
Also, the 257 Bob is downloaded in factory loads, so too is it's parent the 7x57 Mauser. Either case loaded in Europe has much higher pressure, on par with the 30-06 roughly.
When talking about 'improved cases', the extra case capacity is supposed to give the higher velocity, pressure is SUPPOSED TO STAY THE SAME AS THE PARENT ROUND.
I have a couple of AI cartridges, 22-250 AI and 257AI, I run both at the same pressures as the parent cases, except for the 257, I have brought pressures up to 60, 000psi in my loads. Having a Pressure Trace allows me to do this, but even before I owned it, I was loading until excessive pressure signs would exhibit, then back off 3%. Those loads, after pressure testing, were still above 60, 000psi, so I dropped them back another 2%, which brought them just under 60, 000psi.
If original 257 Bob brass, without the so-called +P web thickness increase, can withstand those pressures, why is it loaded to around 40, 000psi by the factories?
I've never understood this.
Without pressure testing equipment, the only way to know that you're loading safely, is either with tested published data, or a program like Quickload, but it must be understood that QL is NOT a substitute for published data, it only PREDICTS the pressure generated from the PARAMETERS YOU FEED INTO IT.

Cheers.
lightbulb

 

[Mikecr]

Pressure trace is no more calibrated than QL.
Both are pretty good once you've validated that you can actually predict results with them.

But 'safe', and 'problem' will always remain independent of pressure in itself.
It really is best to focus on your local condition, as working up & watching what's going on is always best.

 

[hemiford]

Thank you much, Gentlemen !

I believe I understand the gist of this.

So, strictly as an example, if it is stated that 500 Jeffrey derivatives
can be run at a higher pressure than 505 Gibbs derivatives, because
that's what the parent cases are rated at, what am I to believe ?
Or, 408 C-T stuff can be run at a higher pressure than 416 Barrett stuff.

Folks, I'm not stepping on anyone's toes, I just want to understand
the truth of the situation and the logic.

 

[Mikecr]

So, strictly as an example, if it is stated that 500 Jeffrey derivatives
can be run at a higher pressure than 505 Gibbs derivatives, because
that's what the parent cases are rated at, what am I to believe ?
Or, 408 C-T stuff can be run at a higher pressure than 416 Barrett stuff.

Consider why and how max pressures would compare. Each of these cartridges present different chamber areas(h20 capacities). The 500J is smaller than the 505G, the 408CT is smaller than the 416B. The smaller the chamber area, the lower the forces applied, given an example xxxxxPSI.
A larger diameter chamber also means less barrel steel around it, given an example action potential.
A cartridge lower in shoulder angle + higher in body taper + higher in case head area produces greater bolt thrust and lower functional survivability of the brass.

As far as recent cartridges, I suspect their maximum pressure ratings are merely paid for, and with submitted anecdotal evidence for backing basis..
But we'll see for ourselves

 

[elkaholic]

The truth is, 90% of hand loaders do not necessarily know what pressures they are reaching, or go by saami pressures when loading factory chambers either. As has already been mentioned, actions, brass, etc, all affect what is safe and saami has to be all inclusive for anything the cartridge might be chambered in so there is a fair amount of wiggle room depending on what your personal combination is. The manuals are carefully written with a lot of good data and that is all most of us have to go by. Not many people have pressure testing barrels........Rich

 

[MagnumManiac]

Pressure trace is no more calibrated than QL.
Both are pretty good once you've validated that you can actually predict results with them.

But 'safe', and 'problem' will always remain independent of pressure in itself.
It really is best to focus on your local condition, as working up & watching what's going on is always best.

I don't think so.
QL is nothing more than a theoretical program, Pressure Trace gives absolute pressure as measured, I do not understand your reference to it being calibrated. Calibrated to what?
I have tested factory ammo in several different chamberings, very few are at or even near maximum pressure, so what am I supposed to 'calibrate' it too?
If it shows max pressure as tested, is it somehow incorrect in your wisdom?
Although it measures pressure differently to the ammo labs, it still measures pressure.
Even if I could purchase reference ammo, it will NOT measure the same as THAT pressure barrel, so, I don't see your point, Mikecr.

Cheers.

 

[MagnumManiac]

Thank you much, Gentlemen !

I believe I understand the gist of this.

So, strictly as an example, if it is stated that 500 Jeffrey derivatives
can be run at a higher pressure than 505 Gibbs derivatives, because
that's what the parent cases are rated at, what am I to believe ?
Or, 408 C-T stuff can be run at a higher pressure than 416 Barrett stuff.

Folks, I'm not stepping on anyone's toes, I just want to understand
the truth of the situation and the logic.

This has to be understood, EARLY 505 Gibbs BRASS was rated at 40, 000psi max, this matched what is was LOADED to originally. Modern 505 brass is rated the SAME as 408 Chey-Tac brass, the brass companys aren't going to use different drawing/extrusion dies to do different brass internally when it's the same externally, only final necking and length trimming changes.
This was another reason why I went for the 505 Gibbs over the Jeffrey, I can load it to much higher pressure than originally intended. I have already pressure tested loads with a 600gr Woodleigh at 2350fps at being just above 50, 000psi, 2600fps should be posiible, probably not feasible due to thevrecoil, but it can be done. The 500 Jeffrey would not be able to match this.
As Kirby Allen has demonstrated, either the Gibbs or Rigby brass, in modern rifles, will withstand some pretty high pressures, even though as originally loaded they were quite low pressure rounds.

Cheers.
gun)

 

[Mikecr]

QL is nothing more than a theoretical program, Pressure Trace gives absolute pressure as measured, I do not understand your reference to it being calibrated. Calibrated to what?

QL calibration is relative to local chronograph results, leading to prediction capabilities for pressure, and way more than just pressure.
Without a test barrel and a standard ammo, pressure trace can be calibrated no better. In fact, just the same as QL, using the same math to bias the numbers, after measuring results across a chronograph.

If you had a test barrel and a standard for ammo, you could calibrate pressure trace to read known pressure at expected/known velocities(confirmed with a chronograph). From here you could change one thing(the ammo) and results would hold as calibrated.
I can do this with QL, with my standard the chronograph and set barrel & hard ammo parameters(which is all you actually have for pressure trace). From here(locally calibrated) I can change variable ammo parameters and the chronograph will agree.
Given this, pressure to result calculation is pretty straight forward.

 

[Lefty7mmstw]

QL calibration is relative to local chronograph results, leading to prediction capabilities for pressure, and way more than just pressure.
Without a test barrel and a standard ammo, pressure trace can be calibrated no better. In fact, just the same as QL, using the same math to bias the numbers, after measuring results across a chronograph.

If you had a test barrel and a standard for ammo, you could calibrate pressure trace to read known pressure at expected/known velocities(confirmed with a chronograph). From here you could change one thing(the ammo) and results would hold as calibrated.
I can do this with QL, with my standard the chronograph and set barrel & hard ammo parameters(which is all you actually have for pressure trace). From here(locally calibrated) I can change variable ammo parameters and the chronograph will agree.
Given this, pressure to result calculation is pretty straight forward.

One thing that pressure trace is significantly better at than quickload... I can shoot factory ammo through my rifle with pressure trace and match or stay below the pressures generated by the factory ammo. You will never be able to do this with quickload as long as factory ammo uses non-canister powders.

If shooting a true wildcat the two are very similar in capabilities. Instead of psi with pressure trace you may as well call the unit of measure "grapefruit" or something... You are measuring 58,000 grapefruit with load A and 61,500 grapefruit with load B. The only thing certain is most brass starts to deform when you get much beyond 70 Kpsi so you will eventually see the over pressure...

 

[MagnumManiac]

QL calibration is relative to local chronograph results, leading to prediction capabilities for pressure, and way more than just pressure.
Without a test barrel and a standard ammo, pressure trace can be calibrated no better. In fact, just the same as QL, using the same math to bias the numbers, after measuring results across a chronograph.

If you had a test barrel and a standard for ammo, you could calibrate pressure trace to read known pressure at expected/known velocities(confirmed with a chronograph). From here you could change one thing(the ammo) and results would hold as calibrated.
I can do this with QL, with my standard the chronograph and set barrel & hard ammo parameters(which is all you actually have for pressure trace). From here(locally calibrated) I can change variable ammo parameters and the chronograph will agree.
Given this, pressure to result calculation is pretty straight forward.

I still disagree with you.
Just because you CAN change parameters to MATCH results, it still IS NOT measuring your ACTUAL PRESSURE. QL doesn't KNOW every parameter of your barrel, how tight or loose it is, number of grooves and their size and depth, as well as your chamber condition, throat length or any other parameter that differs from it's algorithms. SAAMI pressure barrels are held to very tight tolerances, so even a match barrel isn't going to match SAAMI parameters, therefore no correlation can be reached between their results and mine, or yours.
As I have stated in earlier threads regarding Pressure Trace, I do NOT calibrate to factory ammo, or any other ammo. There are no 'fudge factors', what it reads, is what pressure the ammo is creating.
Maybe I'm doing it wrong, but I have read the FULL info that was supplied, several times, especially the part about WHERE to mount the crystal so that it gives similar placement as to where SAAMI takes it's readings.
I could also place it where CIP read there's, but apparently it will be very different and cause misnomers between the 2 types of systems.

I'm still confused HOW altering parameters until the readings from a chronograph somehow magically match what QL says, is a fact.

Cheers.