223 vs 556

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walterelm

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I have read many times that there are different SAAMI standards for .223 and for. 5.56 NATO concerning pressure.

I do find SAAMI data on behalf of .223, unfortunately only in CUP. I dont find any SAAMI data for the 5.56.

Could someone please help?
 
First up 5.56x45 NATO is not a SAAMI cartridge and thus will not have a SAAMI spec. 223 Remington SAAMI MAP spec is 52,000 CUP or 55,000 PSI (transducer). This will cause arguments but 5.56 NATO and 223 Remington have basically the same maximum pressure specification (at least as US users are concern). Both are rated at 55,000 psi (transducer as SAAMI and the US military would measure it, NATO uses a very different method and thus has a different pressure spec). The difference are in the chamber dimensions not the max pressure.

ETA: Since the OP is in Germany the CIP specification might also have some bearing here. They use a third method to measure pressure and thus a different specification.

Three different (four if we count CUP) methods for measureing the pressure makes this really messy if you get into the details. In reality it probably does not matter that much as long as you understand how your chamber dimensions will interact with your chosen load/bullet.
 
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My head hurts every time I try to understand this...
First up 5.56x45 NATO is not a SAAMI cartridge and thus will not have a SAAMI spec. 223 Remington SAAMI MAP spec is 52,000 CUP or 55,000 PSI (transducer). This will cause arguments but 5.56 NATO and 223 Remington have basically the same maximum pressure specification (at least as US users are concern). Both are rated at 55,000 psi (transducer as SAAMI and the US military would measure it, NATO uses a very different method and thus has a different pressure spec). The difference are in the chamber dimensions not the max pressure.

ETA: Since the OP is in Germany the CIP specification might also have some bearing here. They use a third method to measure pressure and thus a different specification.

Three different (four if we count CUP) methods for measureing the pressure makes this really messy if you get into the details. In reality it probably does not matter that much as long as you understand how your chamber dimensions will interact with your chosen load/bullet.
 
The answer to your question will be more relevant if we know more about your reason for asking. Firing factory or surplus ammo? Reloading with .223 or 5.56 brass? Which case is your gun chambered for?
 
Once you’re reloading, there’s no difference between the two. You’re going to seat the bullets to the shorter of your desired jump to lands or mag length, and going to load powder to whatever level your rifle tells you is its max. It’s not even really fair to say 5.56 brass is always thicker than 223 brass, as that simply hasn’t proven true for all brass throughout even recent history. So the point is moot if you aren’t shooting factory ammo.

Even firing factory ammo, as long as I’m not jamming in the lands, I don’t sweat the difference.
 
Well ... indeed i live in germany ... i did shoot some military surplus ammo through my mini 14 and just wondered why in us forums there is so much concern about shooting 5.56 nato in a .223 chambered rifle.

The legal situation in germany, a C.I.P. member, is this: surplus military ammo is proof tested for .223, relabeled as .223 and thats it. Apparently the pressure debate is a non debate, as military surplus ammo in 5.56 nato just does not have too much pressure when tested according to C.I P. specifications. BTW: there is no 5.56 Nato spec in C.I.P. thats why it has to be proofed before ....

Now the dimensions of the cartridge: C.I.P. appears to have large tolerances, thats why 5.56 nato just fits into .223 C.I.P. specs.

That said: i do have a howa 1500 in .223 where i couldnt fire surplus ammo ... the bold just didnt close. But this gun is also a tricky one with reloaded ammo so ....
 
@mcb
SAAMI and C.I.P. use the same transducer from the same swiss company for measuring pressure (psi or bar). But the placement of the transducer differs.

The military uses still another placement because they want to spent less time on each measurement.

The CIP proofing of ammo requires a hole to be drilled into the cartridge to place the transducer. Here the actual pressure in the cartridge is measured. I dont know about SAAMI ... but that doesnt matter. Indeed ammo will deliver different results when testes according to SAMMI and test accirding to CIP. I believe ... dont know ... that for a given ammo the CIP value is allways higher than the SAAMI pressure value.

When american ammo is sold in europe it passes with no problems the cip proofing. I am told no ammo certified to meet SAAMI spec will ever be too powerfull for C.I.P.

When Geco started producing 9mm ammo for IPSC for the european market, they stayed within the limits of CIP but approached the upper limit. Til then 9mm IPSC shooters relying on factory ammo would fail from time to time the needed factor of 125. Now there is an ammo that meets the requirements. I am told that this ammo is sold on the US market as +P. I guess Geco uses a different brand in the US.

That is why i asked about SAAMI specs concerning pressure. If a US manufactured rifle hits the european market it will be CIP proofed. And i am pretty sure they dont make any differences when producing a rifle wether it stays in the US or goes oversea. So why should there be any concern regarding pressure using 5.56 in .223 in the US if the rifle will meet cip requirements wether it is proofed or not.
 
@mcb
SAAMI and C.I.P. use the same transducer from the same swiss company for measuring pressure (psi or bar). But the placement of the transducer differs.

The military uses still another placement because they want to spent less time on each measurement.

The CIP proofing of ammo requires a hole to be drilled into the cartridge to place the transducer. Here the actual pressure in the cartridge is measured. I dont know about SAAMI ... but that doesnt matter. Indeed ammo will deliver different results when testes according to SAMMI and test accirding to CIP. I believe ... dont know ... that for a given ammo the CIP value is allways higher than the SAAMI pressure value.

When american ammo is sold in europe it passes with no problems the cip proofing. I am told no ammo certified to meet SAAMI spec will ever be too powerfull for C.I.P.

When Geco started producing 9mm ammo for IPSC for the european market, they stayed within the limits of CIP but approached the upper limit. Til then 9mm IPSC shooters relying on factory ammo would fail from time to time the needed factor of 125. Now there is an ammo that meets the requirements. I am told that this ammo is sold on the US market as +P. I guess Geco uses a different brand in the US.

That is why i asked about SAAMI specs concerning pressure. If a US manufactured rifle hits the european market it will be CIP proofed. And i am pretty sure they dont make any differences when producing a rifle wether it stays in the US or goes oversea. So why should there be any concern regarding pressure using 5.56 in .223 in the US if the rifle will meet cip requirements wether it is proofed or not.

SAAMI and CIP use very different methods to measure the pressure. Mega rambling warning.

SAAMI pressure testing for the current Transducer method uses a piezo force sensor (from PCB Piezotronics) attached to a conformal post of a precise diameter that extends through a matching hole the pressure test barrel and touches the outside of the cartridge case (thus nearly every cartridges has to have a cartridge specific sensor assembly, though some family of cartridges share sensors ie 243 Win, 260 Rem, 308 Win ). It is typically located forward of the middle of the case but behind the shoulder if the cartridge has one. When fired the pressure pushed on the case wall that pushes on this force sensor. Pressure is inferred from the force measurement. A calibration method/apparatus exists to correlate actual chamber pressure to the force and compensate for the brass thickness over the sensor post. But because this measurement is made through the case wall you have to use new brass and the brass has to all from the same batch both your empty calibrate cartridges for calibration and your actual test lot of ammo. SAAMI pressure testing on reloaded brass introduces a lot more error due to variation in residual brass hardness from previous firings. The advantage of the SAAMI method is the sensor is well protected and after calibration testing proceed fairly quickly without special holed ammunition. The US military method is based directly on the SAAMI method and uses the same hardware.

Series_117B_Application.gif

The much older SAAMI Crusher method is located in a similar location on the side of the case but uses a cartridge with a hole in it (thin tap applied to retain powder). The hole in the case has to be aligned to a hole in the test barrel. This allows allows pressure to push on a gas check (gas seal) that pushes on an piston that acts on the crusher (a cylindrical piece of very pure annealed copper or lead made to very precise dimensions). Pressure is then inferred from how much crush (change in length) is measured in the crusher. Each batch of crushers comes with a calibration chart that correlates change in length to a peak pressure. This method is still in use by a surprising number of companies but it is moderately expensive (due to consumable crushers) and very slow and tedious to conduct.

images?q=tbn%3AANd9GcSG_5Y0GS51DyOpAGTuAwzJV_-4BnV55iU-VnVJUbj3UEX6gqU1&usqp=CAU.jpg

The CIP method is similar to crusher in that it uses a cartridge with a hole drilled in it at a specified location. The hole is aligned with a port in the pressure barrel but unlike the crusher method the gases act directly on a piezo pressure sensor (Kistler) and unlike SAAMI CIP measures pressure directly. In the picture below the CIP sensor would be the left one. CIP has the advantage of probably being the most true chamber pressure vs time data curve. The problem with CIP is it takes special holed cartridges and since the sensor is directly expose to hot propellant gases, sensor life is shorter than the SAAMI method The NATO EPVAT method uses a similar direct pressure sensor like CIP but it located at the case mouth as shown by the right sensor in the picture below. This has the advantage of not needed holed ammunition but it misses the the earlier part of the pressure curve that happened before the bullet moves past the sensor location.

images?q=tbn%3AANd9GcQ0clwS___HbtMWaVVfV15qyovNHAcUqIkSQdrhpRL-DTEZiD1C&usqp=CAU.png

But I agree the SAAMI spec for nearly all cartridges shared between CIP and SAAMI will easily pass the CIP method. You cannot directly compare SAAMI transducer specs to CIP transducer spec. Though there is a very strong correlation and you can create reasonable accurate conversion between CIP and SAAMI transducer methods but even that is somewhat error prone. Correlation/Conversion between any of the traducer methods with the older CUP/LUP are not advised and full of weird errors.

Measuring pressures that are this high and this transient is very difficult and the method still has far more effect on the measurement than most people what to admit. I know US ammo companies that despite the SAAMI transducer method being faster, cheaper and easier to do still use the Crusher method on ammo if the ammo predates the acceptance of the transducer method. Not because the Crusher method is better, it's not, with many short comings, but it is very repeatable and producing consistent ammo is more important than going to a new measurement method.
 
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@mcb ... wow ... this information is normally spread over several different sites. I have never seen all different methods put together like this.

It would have been odd if CIP and SAAMI would indeed use the same transducer of swiss proveniance.

But ...i guess the old CUP measurements and the new pressure measurements (both SAAMI) are equally "repeatable". But the shortening of a copper cylinder is easier to interprete than the data gathered from the transducer. Thats why so many companies stick with cup. (I guess ...)
 
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@mcb ... wow ... this information is normally spread over several different sites. I have never seen all different methods put together like this.

It would have been odd if CIP and SAAMI would indeed use the same transducer of swiss proveniance.

But ...i guess the old CUP measurements and the new pressure measurements (both SAAMI) are equally "repeatable". But the shortening of a copper cylinder is easier to interprete than the data gathered from the transducer. Thats why so many companies stick with cup. (I guess ...)

It has taken me quite some time to get all the methods straight in my head too, and I may not have it 100% right but I think I am close. That said I am very familiar with SAAMI transducer method but the other methods I have less direct exposure and it's mostly from reading not actual exposure to the process.

The CUP method is harder and slower to do then the Tranducer method and requires a little more operator skill to do it well but since the company had worked up all these old loads using the CUP method they stick with it. In practice the transducer method is much easier and gives you more data (the full pressure vs time curve instead of a single data point representing the peak pressure) but it more about consistency than ease of method at least for a production setting for these old companies. Don't get me wrong most of the ammunition companies are using the transducers methods for all of their testing but I know of one or two of the older US ammo makers that are still using the CUP method for older cartridges. There are a few old cartridges that don't have a transducer spec since they are nearly obsolete. For example 250 Savage and 30-40 Krag don't have transducer specs only CUP specs.
 
As far as shooting 5.56 ammo in rifles with a true .223, it can cause issues depending on how the chamber was cut (how close to true specs). It also depends on what type of rifle. I had a H&R Handi-Rifle (break open single shot)chambered in 223 and 5.56 ammo was too much for it. The H&R action would pop open when fired with surplus 5.56 but was fine with factory 223 ammo.
 
I give Gunny credit for this; he posted it a while back. I keep it on my phone for quick explanations at the range:

223 vs 5.56.jpg

Doesn't explain the differences between psi, lup, and cup well, but it shows why the pressure differences can develop.


As far as shooting 5.56 ammo in rifles with a true .223, it can cause issues depending on how the chamber was cut (how close to true specs). It also depends on what type of rifle. I had a H&R Handi-Rifle (break open single shot)chambered in 223 and 5.56 ammo was too much for it. The H&R action would pop open when fired with surplus 5.56 but was fine with factory 223 ammo.

I had the same thing happen with both Handi-Rifles I had in .223.
 
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