PSI Max

[223ai]

All -

Can anyone give me some feedback as to what is considered maximum pressure in a .223 bolt gun? I completely understand that my rifle will tell me what is considered maximum pressure.

I'm curious to know if people are running closer to 70k in their bolt guns with 75-90gr bullets.

Thanks,
Josh

 

[ChadTRG42]

Re: PSI Max

Bolt guns chambered in 223 Rem are rated at ~52,000 psi. AR-15 with a 5.56 chamber are rated at ~62,000 psi. It depends on your bolt rifle, but I've seen pressure just above 223 Rem pressures. I've seen mil spec 5.56 ammo be too hot for a bolt gun. I always try to run an incremental increase in powder 1 round at a time with the components I plan on shooting to see where I get pressure, and then load some test loads under this max to see how it shoots.

 

[BobinNC]

Re: PSI Max

SAAMI Max Pressure for a .223 Rem is listed @ 55,000 PSI

Link:

SAAMI Max Pressures

C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portativeslists) lists .223 Rem Max pressure as 62,366 PSI. This is the same service pressure rating as the 5.56x45mm NATO.

Here is a link comparing SAAMI pressure ratings compared to C.I.P. ratings:

Cartridge Pressure Standards

 

[223ai]

Re: PSI Max

It's interesting to me that, while I have no tools to measure actual PSI, QL is showing my 223ai pressure at 70k psi with the corresponding bullet speed. I have zero pressure signs, and am on my 8th firing of the brass, with one annealing cycle.

 

[9H_Cracka]

Re: PSI Max

Josh, we are all just pissin' in the dark tryin' to miss our shoes without a strain gauge system:

http://riflemansjournal.blogspot.com/2011/02/cartridges-long-range-reloading-safety.html

 

[Jerkface11]

Re: PSI Max

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JPipes</div><div class="ubbcode-body">It's interesting to me that, while I have no tools to measure actual PSI, QL is showing my 223ai pressure at 70k psi with the corresponding bullet speed. I have zero pressure signs, and am on my 8th firing of the brass, with one annealing cycle.


</div></div>

AI cartridges have a sharp shoulder angle and almost no body taper. That keeps them from showing "pressure signs".

 

[The Mechanic]

Re: PSI Max

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JPipes</div><div class="ubbcode-body">It's interesting to me that, while I have no tools to measure actual PSI, QL is showing my 223ai pressure at 70k psi with the corresponding bullet speed. I have zero pressure signs, and am on my 8th firing of the brass, with one annealing cycle.</div></div>
Make sure you do a water test on those fired and cleaned (un-resized) cases. You will get a MUCH better idea of the pressure you are getting with QL

 

[Clark]

Re: PSI Max

The 223 pressure limitation is the case head, getting a loose primer pocket. The threshold of loose primer pocket with one firing vs 10 firings seems to be separated by ~ 5,000 psi in Quickload predictions.

a) The 1950 designed .222 case head is good for more pressure than the 1889 7.65x53mm Mauser case head made with large Boxer primer [e.g. .308 Win].
b) The .222 case head is good for a little more than the 1925 designed 300 H&H case head [e.g. 300 Win Mag].
c) The .222 case head is not good for as much pressure as the 1978 designed small primer pocket Mauser case head in the 6mmBR.

Hodgdon website: 223 Rem, H335, 25.3 GR. 55 GR. SPR SP, 2.200", 24" barrel, 3203 fps, 49,300 CUP

Test: Ruger #1, CCI 400 small rifle primers, LC brass once fired processed from Scharch and prepped by me, 55 gr Vmax moly, H335

pic left to right: unfired, 28, 29, 30, and 31 gr.
a) unfired, extractor groove .329"
b) 28 gr, extractor groove .329", 11% overload 69 kpsi Quickload
c) 29 gr, extractor groove .329", 15% overload 80kpsi
d) 30 gr, extractor groove .3295", 19% overload 92kpsi
e) 31 gr, extractor groove .3320", 23% overload 106kpsi

This would indicate that a single time event to reach yield for the .222 case head [.223] that I tested corresponds to a Quickload estimate of between 80kpsi and 92 kpsi chamber pressure.

This question was later analyzed by Scott Sweet for me, a guy who does Von Mises for a living:

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">22 June 2004 07:43
Clark,
Here are the results of the von Mises stress calculations for the 223
Remington case head.
Using mechanical properties for C26000 brass (cartridge brass)
Temper - H06
Tensile yield strength - 65,300 psi
von Mises stress at the Primer pocket surface - 117,186 psi
von Mises stress at the Extractor OD - 65,300 psi (initiation of yielding)
Chamber pressure - 86,427 psi (Nominal properties)
Chamber pressure - 80,809 psi (minimum properties)
Chamber pressure - 92,044 psi (maximum properties)
Again these values are ONLY valid for a H06 tempered C26000 case.[Scott Sweet]</div></div>

While the testing with H335 is predictable, stable, and repeatable, the testing with Blue Dot is erratic.

Here we see a number of 223 case heads all fired with 18 gr Blue Dot 33 gr Vmax. The intact brass measured 4100 fps, and the destroyed brass measured 4200 fps. The pressure varies so much with this load that associating a single pressure with the load has no meaning.

Here we see 18 gr Blue Dot 33 gr Vmax fire in an AR15.
We see pressure signs:
1) The case head web is about to break from the body.
2) The outline of the extractor is visible on the case head.
3) The outline of the ejector is visible on the case head.
4) The primer is cratering back through the gap between firing pin and firing pin hole.

I have done long term experiments at 66kpsi with large populations of brass dedicated to a particular sizing die. Full length sized with shoulder set back that will accommodate the different headspace measurements on factory rifles makes for trimming brass every firing or ever other firing. However, 20 consecutive firings are possible with neck sizing at 66 kpsi before trimming is necessary. .223 brass shrinks too much on firing at high pressure and grows too much on FL sizing.

What does it all mean?
a) The .223 is SAMMI registered at 55k psi max average pressure and 71.5 kpsi to 77 kpsi proof pressure.
b) The cartridge is empirically and analytically has a threshold of long brass life ~ 80 kpsi and a threshold of short brass life ~ 85 kpsi.
c) Full length resizing of the brass for AR15s may preclude using the .223 at higher pressures as the trim frequency is too high.

 

[The Mechanic]

Re: PSI Max

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Clark</div><div class="ubbcode-body">The 223 pressure limitation is the case head, getting a loose primer pocket. The threshold of loose primer pocket with one firing vs 10 firings seems to be separated by ~ 5,000 psi in Quickload predictions.

a) The 1950 designed .222 case head is good for more pressure than the 1889 7.65x53mm Mauser case head made with large Boxer primer [e.g. .308 Win].
b) The .222 case head is good for a little more than the 1925 designed 300 H&H case head [e.g. 300 Win Mag].
c) The .222 case head is not good for as much pressure as the 1978 designed small primer pocket Mauser case head in the 6mmBR.

Hodgdon website: 223 Rem, H335, 25.3 GR. 55 GR. SPR SP, 2.200", 24" barrel, 3203 fps, 49,300 CUP

Test: Ruger #1, CCI 400 small rifle primers, LC brass once fired processed from Scharch and prepped by me, 55 gr Vmax moly, H335

pic left to right: unfired, 28, 29, 30, and 31 gr.
a) unfired, extractor groove .329"
b) 28 gr, extractor groove .329", 11% overload 69 kpsi Quickload
c) 29 gr, extractor groove .329", 15% overload 80kpsi
d) 30 gr, extractor groove .3295", 19% overload 92kpsi
e) 31 gr, extractor groove .3320", 23% overload 106kpsi

This would indicate that a single time event to reach yield for the .222 case head [.223] that I tested corresponds to a Quickload estimate of between 80kpsi and 92 kpsi chamber pressure.

This question was later analyzed by Scott Sweet for me, a guy who does Von Mises for a living:

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">22 June 2004 07:43
Clark,
Here are the results of the von Mises stress calculations for the 223
Remington case head.
Using mechanical properties for C26000 brass (cartridge brass)
Temper - H06
Tensile yield strength - 65,300 psi
von Mises stress at the Primer pocket surface - 117,186 psi
von Mises stress at the Extractor OD - 65,300 psi (initiation of yielding)
Chamber pressure - 86,427 psi (Nominal properties)
Chamber pressure - 80,809 psi (minimum properties)
Chamber pressure - 92,044 psi (maximum properties)
Again these values are ONLY valid for a H06 tempered C26000 case.[Scott Sweet]</div></div>

While the testing with H335 is predictable, stable, and repeatable, the testing with Blue Dot is erratic.

Here we see a number of 223 case heads all fired with 18 gr Blue Dot 33 gr Vmax. The intact brass measured 4100 fps, and the destroyed brass measured 4200 fps. The pressure varies so much with this load that associating a single pressure with the load has no meaning.

I have done long term experiments at 66kpsi with large populations of brass dedicated to a particular sizing die. Full length sized with shoulder set back that will accommodate the different headspace measurements on factory rifles makes for trimming brass every firing or ever other firing. However, 20 consecutive firings are possible with neck sizing at 66 kpsi before trimming is necessary. .223 brass shrinks too much on firing at high pressure and grows too much on FL sizing.

What does it all mean?
a) The .223 is SAMMI registered at 55k psi max average pressure and 71.5 kpsi to 77 kpsi proof pressure.
b) The cartridge is empirically and analytically has a threshold of long brass life ~ 80 kpsi and a threshold of short brass life ~ 85 kpsi.
c) Full length resizing of the brass for AR15s may preclude using the .223 at higher pressures as the trim frequency is too high.</div></div>
DANG!!!
Should I assume that would be eye protection mandatory?

 

[Clark]

Re: PSI Max

This was sent to me after someone got hurt.

It seems like a low pressure load with case head failure caused by previous stretching.

The nearly new Rem700 223 put the gas right in his eye.

I have never shot a Rem700 since then without eye protection.

 

[vman]

Re: PSI Max

Clark, that is truly terrifying!

I always wear safety glasses for this very reason.

Very interesting read in this thread.

Consider this a tag.

 

[500grains]

Re: PSI Max

Art Alphin of A-Square sayeth you cannot make definitive conclusions about pressure from brass condition or brass expansion measurements because of the enormous variation in quality and hardness of brass from Bertram (not so good) to Lapua (the best IMO).

As for the 2nd case in Clark's lineup, well, I wear motorcycle goggles at the shooting range, not just glasses, for that very reason.

One of these days Clark will post 3 photos on here. One photo will show his head with half of his face blown off. The next photo will show the pieces of his rifle, which blew up like a hand grenade. The third photo will show the other half of Clark's face 25 yards back from the firing line, having come to rest on the hood of his car.

Here is an artist's concept of what Clark will look like afterwards (NSFW):

http://dashowcase.com/wp-content/uploads/2009/08/face-blown-off-firecracker-02.jpg

NSFW

 

[223ai]

Re: PSI Max

Clark -

EXTREMELY interesting, thank you for taking the time to write that up. I am not an engineer, so your conclusions helped sum up the post for me. If I am following you properly, 55k psi max is conservative, and anything above 82k psi is getting into dangerous territory for obvious reasons? If I may ask, at what predicted pressure do you run your 223 loads?

Thanks,
Josh

 

[Clark]

Re: PSI Max

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 500grains</div><div class="ubbcode-body">

One of these days Clark will post 3 photos on here. One photo will show his head with half of his face blown off. </div></div>
And I will still look better than 500G.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">JPipes
'' at what predicted pressure do you run your 223 loads?
Josh</div></div>
For deer/elk/antelope with Mauser case head or belted magnum case head I run 4% less powder than the threshold of long brass life.

For ground squirrels in 223 I do 15 gr Blue Dot 33 gr Vmax 3500 fps 35,000 psi. This is basically a .223 downloaded to 218 Bee. I have shot thousands of these rounds. The barrel stays cool and clean. It will not cycle an AR15, but gets the job done single shot.

I would not be afraid to load up large quantities of 223 at 4% less powder than threshold of long brass life with H335, but I am not going to do it with erratic Blue Dot.