Risk of shooting factory 5.56 ammo in a .223 chamber?

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jmr40 said:
Before the internet the 2 were used interchangeably. Yes, the 5.56 if loaded to its full potential is somewhat hotter than 223. But no more so than any other ammo cartridges. You'll see a much wider range of pressures in 30-06 than you will between 223 and 5.56. We could easily break down 30-06 loadings into 3-4 different classes but we don't.
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No, they weren't, Ruger always recommended not shooting military stuff in Mini-14s....
 
tark said:
I have heard, and read, that Nato ammo is loaded to higher pressures. Compounding this, Nato chambers are cut differently than 223 chambers. In the nato chamber there is a bit of space from the end of the case to the point where the bullet actually bites into the rifling. (Or the other way around!) This lowers pressures a bit, which ALLOWS the Nato ammo to be loaded to higher pressures. When you shoot Nato in a 223 chamber, that freebore is absent, and pressures can spike.

Or so they say. Can't always believe what you read and hear, but that explanation seems to make sense.
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One - There is no such thing as a "5.56mm NATO" chamber. There is an M16 chamber, and M249 chamber a C7 chamber, a G36 chamber, etc., etc., even the test barrel used to test military ammunition is not the same as any of the various rifle chambers.

And even among the "M16" family will all the different civilian barrel makers out there, there is a wide variety of chambers all marked "5.56 NATO" on the barrel.

In general, the military chamber have a longer freebore, the cylindrical portion of the bore prior to the start of the rifling. This allows the bullet to get a 'run-and-go' at the rifling reducing the pressure needed to engrave the rifling on the bullet.

TWO - There is no such thing as "NATO pressure". STANAG 4172 specifies that the chamber pressure of standardized ammunition shall not exceed an average pressure of 380 Mpa (55,114 psi) with a average plus three standard deviations of 420 Mpa (60,915 psi). But, US ammunition is not made to STANAG specifications regarding pressure, and judging from pressure tests on various lots of foreign ammunition, few other countries are either.

So, let's look at some available ammunition and their maximum average pressures specified:

M193 (MIL-C-9963) = 55,000 psi
SAAMI (ANSI-SAAMI-2299.4-1992) = 55,000 psi
STANAG 4172 = 55,114 psi
M885 (MIL-DTL-63989) = 58,700 psi.

.223 Remington and M193 Ball are loaded to the same pressures and M855 Ball is slightly higher. Most of the measured pressure difference people see when firing military ammunition in .223 Remington chambers is due the throat differences, not "because military ammunition is loaded hotter".

The often quoted C.I.P. pressure for 5.56mm x 45 of 62,000 psi cannot be directly compared to the above as it is not the maximum average, but it is a statistical cut-off number that ensure no load exceeds that pressure, backing out the average from that cut-off and assuming a standard deviation similar to military ammunition yields a maximum average around 55,000 to 56,000 psi, similar to SAAMI and M193.

And, nobody is using C.U.P. pressure measurement anymore, so please, nobody bring that up...
 
The larger anecdotal set of kabooms discussed on the internet shows that most AR's which have issues are based on bolt bounce due to high cyclic speeds, induced by gas port locations inappropriate to that barrel length.

AR gas ports are timed 5 inches back from the muzzle, carbine gas on a 16" is the most notorious abuse and it is still available. Yet nobody seems to care much even tho the aftermarket industry went out of their way to invent mid length for NFA legal barrels.

Most of the discussions of kabooms then devolve to handloads or import ammo with dubious reputations. So it goes - just exactly how many .223 rifles get blown up with the inadvertent use of NATO 5.56 ammo? It's apparently so small and hard to determine that only internet posters bother to argue over it - and the argument continues since the invention of the internet.

I would speculate more people take bigger risks driving to work in the morning commute. Simple comparison - we record traffic statistics, compare them to the known number of Kabooms shooting 5.56 in a .223. Right. NO DATA.

It happens so rarely we don't even keep stats on it. No recalls, just liability warnings in the owner's manual to stop speculative claims being held against the maker.

Unless you have the test fixture to proof your rounds, I dare say some handloaders are pushing their hotter loads up to 62,000 and their specific combinations won't show overpressure there, either. If it's isn't measured, then it cannot be categorically denied it doesn't happen.

Anyway, back to the normal routine of chest thumping and monkey dancing.
 
Sooo.... for the sake of argument....

Everyone that says you can run 5.56 in a .223...

I would love to see a test of a minimum spec .223 chamber and a sharp angled leade , no freebore firing M855A1, and other "full power" ( Fed. Independence early batches, Various years of Winc. ) 5.56 rounds, some of the Carl Gustav surplus, etc.....

I doubt anyone is going to blowup a rifle... but, like I said before... you can also blow primers and case heads.

The point SAAMI is making is valid. Not all 5.56 is equal.... there is plenty of lowered powered 5.56 ammo out there as well... Radway Green was / is underpowered, the current Aussie stuff is underpowered...

Point is, with 5.56 you might be able to "stack" tolerances enough to damage a .223 chambered firearm.

So a blanket statement from SAAMI is logical, there are just to many variables at play to be able to say 5.56 can be SAFELY fired from a .223 chamber rifle.


I'd bet there are just as many people that have had issues with blown primers , etc as have safely done this.... its just that you can't say EVERY rifle can do it.
 
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I'm convinced many people load ammo to higher pressures in their rifles that SAAMI max average specs state. They're using a "rubber ruler" to measure pressure by observing primer flattening and measuring case head expansion. All primer cups and cartridge brass is not the same hardness so a given peak pressure will result in different interpreted levels across all primers and cases for that cartridge.

Belted magnums are probably the most cartridge types loaded over SAAMI specs.

All the above stuff will typically have higher pressures compared to specs than a 5.56 military round fired in a commercial SAAMI spec .223 chamber.

I've shot 7.62 NATO proof loads at 67,500 cup in Garands and showed those fired case to several folks. Most of them said the load was at a normal maximum safe level based on their interpretation of the flattened primer. MIL SPEC pressure was 50,000 cup. The rest said a bit on the warm side but still safe.
 
Quote by lysander;
No, they weren't, Ruger always recommended not shooting military stuff in Mini-14s....

Wrong! read the manual, The only mini ruger does not recomend 5.56 in is their target model.
STW
 

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I have never owned a .223 bolt rifle.

I have owned a few dozen semi autos including AR15's, Mini14's and my Galil. I have absolutely NEVER seen any signs of over pressure in any of them no matter what ammo I use whether factory or my handloads. I have shot up many thousands of rounds of military ammo and just about every type of commercially produced fodder there is. I haven't bothered to shoot the real high end hunting ammo so I have no practical experience with it.

My personal belief it that the whole .223 vs 5.56 debate is all a bunch of internet BS that keeps getting regurgitated ad nausem.
 
LysanderXIII , quit being a grammar Nazi! Everyone knows what I mean when I say 5.56 NATO Chamber.. Besides, if there is no such thing as a 5.56 NATO Reamer, why does the box it comes in say "5.56 NATO?" When I worked for Les, the AR line had three types of chamber reamers, .223, 5.56 NATO and a reamer that Clymer made just for us. Don't remember seeing any other kind.

.223 55,000PSI
M-855 58,700PSI

Those are your figures.....seems to me that the Nato ammo IS loaded to more pressure. Not a huge amount, but more pressure nevertheless.

My Mini-14 is marked, "5.56 NATO", so I assume you must have meant some of the older Minis. (?)
 
I still haven't found any "cheap imported 223" that I wouldn't fire in my AR's. I use mine for shooting stuff like trees, cans, steel plates, lakes and paper targets. I bet I have 50k rounds of "imported cheap 223" through a low end DPMS (oracle I think) and it still goes boom every time. The bump stock burns through ammo.
I have probably run 10k rounds of 5.56 through various guns over the years. No kabooms yet.
 
Quote....

"Speaking of chamber pressure, that’s the other thing that changed. The NATO maximum chamber pressure is 12% higher than the SAAMI .223 Remington maximum chamber pressure. However, due to the way in which those chamber pressures are measured (NATO measures at the throat, SAAMI does not) the pressures aren’t exactly the same. Nevertheless, the common belief is that 5.56 NATO pressures are higher than .223 Remington pressures.

Due to the difference in throat length and chamber pressure, the conventional wisdom is that .223 Remington ammo is safe to fire through a 5.56 NATO gun, but not necessarily the other way around. But due to the different throat length, the .223 Remington ammunition won’t be as accurate.

There is, however, a compromise. The .223 Wylde chamber that is used in most National Match AR-15 rifles is designed to combine the best of both specifications and work for either caliber. I believe it also has a longer throat than either spec, which means that you can use longer bullets than anything else. But again, longer throat can lead to concentricity issues."


This is what I am saying... the throat length / freebore / leade has a big impact in pressure.
 
The whole .223 vs 5.56 debate is not all a bunch of internet BS that keeps getting regurgitated ad nausem.t

I asked SAAMI about that some years ago. The man I talked with said there are some combinations of 5.56 NATO ammo and .223 Rem chambers that will let peak pressure go over their max average spec for the Remington round. That's their criteria for mentioning all bad combinations in their document seen at:

http://www.saami.org/specifications...1-Unsafe_Arms_and_Ammunition_Combinations.pdf

on page 7 for the 5.56 vs .223 information.
 
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Bart B. said:
The whole .223 vs 5.56 debate is not all a bunch of internet BS that keeps getting regurgitated ad nausem.t

I asked SAAMI about that some years ago. The man I talked with said there are some combinations of 5.56 NATO ammo and .223 Tem chambers that will let peak pressure go over their max average spec for the Remington round. That's their criteria for mentioning all bad combinations in their document seen at:

http://www.saami.org/specifications...1-Unsafe_Arms_and_Ammunition_Combinations.pdf

on page 7 for the 5.56 vs .223 information.
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Still never heard of anything bad happening, nor has anyone here yet reported anything. Just because it slightly exceeds the max average spec doesn't mean something bad will happen. If the gun can take it, it'll be fine. And all modern guns are capable of doing so. This isn't the early days of .223 where there were a number of weaker .222 Remington guns modified to take it. Every manufacturer that makes a .223 firearm knows there's a good chance that someone will use 5.56 in it, and they make it strong enough to ensure it won't blow up.

As I've said before, you're not going to destroy your gun shooting 5.56, although you will add wear and tear to it, primarily to the barrel. Should you make a habit of it? No. But in an emergency situation where that's all you have, it would be fine.
 
I haven't ever seen a 223 blown up by 5.56 ammo, but I have seen a 223 bolt action that had to have the bolt handle hit with a mallet to get the action open after firing surplus military ammo. To me, that says the chamber was too tight for the ammo, or the ammo was loaded too hot, or a combo of both.
 
5.56 X 45 NATO ammo made at arsenals around the world has three or four pressure measuring systems that are different than the SAAMI spec system used in the USA. Equipment and measuring point on the test barrel are at different places. Chamber dimension specs also vary. As do the pressure numbers.
 
I cannot imagine that any mass market gun manufacturer today would sell a gun that fits factory 5.56 and not shoot it safely. There is zero benefit and an enormous amount of legal exposure doing it otherwise. If this is a problem at all, it is probably an extreme situation confined to someone working up a 1,000 yd load in their custom target gun.

I'll believe in these kabooms, the Easter bunny and unicorns -- when I actually see them.
 
I'll believe in these kabooms, the Easter bunny and unicorns -- when I actually see them.
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I never knew there was a difference during my first 15 years of multiple .223 rifle ownership. I must have put thousands of rounds of 5.56 through various .223 rifles and never had a single ammo related malfunction.....
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Rest assured that between the hand wringers and the internet, the myth will remain alive forever
 
I shoot hand loads in both 223 and 5.56 cases out of my savage axis 223. I shoot 5.56 factory ammo and 223 factory ammo. The rifle doesn't care and the pressure signs are non existent. A modern built rifle that wont take either round seems completely ridiculous to me. The lawyers are there to make sure that throat is cut to protect the manufacturer. Your chances of blowing up a modern 223 with 5.56 seem pretty low. If I had somehow accidentally bought an ar-15 with a 223 barrel on it, I would most definitely shoot 5.56 though it. Initially I may monitor brass to watch for any issues but I'd definitely run some through it.
 
While all of this can make for interesting conversation every now and then the areas of chamber pressures for 5.56 NATO verse .223 Remington can get confusing to say the least. The more we read the more conflicting data we find.

For starters SAAMI (Sporting Arms and Ammunition Manufacturers' Institute) is an association of the nation's leading manufacturers of firearms, ammunition and components. SAAMI was founded in 1926 at the request of the federal government and tasked with:

1. Creating and publishing industry standards for safety, interchangeability, reliability and quality

2. Coordinating technical data

3. Promoting safe and responsible firearms use

Looking back at #1 it is important to understand that the SAAMI standards and or specifications are not exactly the law of the land. Thus things are frequently stated as such:
American National Standard Voluntary Industry Performance Standards for Pressure and Velocity of Centerfire Rifle Ammunition for the Use of Commercial Manufacturers
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Voluntary does not imply comply or die to a standard. :)

As to the 5.56 NATO verse the .223 Remington there are pages of text out there including a dozen or more white papers written on the subject. Something to remember or take note of with Chamber Pressure in general is that chamber pressures are always listed or published as a Maximum Pressure. That does not mean every cartridge of .223 Remington or 5.56 NATO will meet or exceed some published number. It also does not mean that number will be a uniform constant across all rifles or more specific chambers.

Looking at chamber pressure alone for the 5.56 NATO cartridge:
Maximum pressure (EPVAT 5.56) 430.00 MPa (62,366 psi)
Maximum pressure (SCATP 5.56) 380.00 MPa (55,114 psi)
Which do you like? Just pick the one you like, they are both chamber pressures for the 5.56 NATO cartridge. Just a matter of how the data is taken or measured:
NATO EPVAT
NATO defines 5.56mm, 7.62mm, 9mm and 12.7mm using the NATO EPVAT test methods, which includes pressure testing. Unlike the civilian testing methods NATO EPVAT testing procedures for the "NATO rifle chamberings" require the pressure sensor or transducer to be mounted ahead of the case mouth. The advantage of this mounting position is that there is no need to drill the cartridge case to mount the transducer. Drilling prior to firing is always a time consuming process (fast quality control and feedback to production is essential during the ammunition manufacturing process). The disadvantage of this mount is that the pressure rises much faster than in a drilled cartridge case. This causes high frequency oscillations of the pressure sensor (approx 200 kHz for a Kistler 6215 transducer) and this requires electronic filtering with the drawback that filtering also affects the lower harmonics where a peak is found causing a slight error in the measurement. This slight error is not always well mastered and this causes a lot of discussion about the filter order, cutoff frequency and its type (Bessel or Butterworth). For the 9mm NATO EPVAT specifies that for 9×19mm Parabellum (9mm Luger in C.I.P. nomenclature and 9mm NATO in NATO nomenclature), the transducer must be positioned at the mid case position (9.5 millimetres (0.37 in)) from the breech face instead of C.I.P.'s 12.5 millimetres (0.49 in) from the breech face. For NATO EPVAT testing of military firearms ammunition NATO design EPVAT test barrels with Kistler 6215 channel sensor transducers are used.
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Pretty sure we get the drift of where the measurement is taken for the EPVAT method.

SCATP is based on the currently used SAAMI method:

SAAMI method
SAAMI pressure testing protocol uses a conformal Piezoelectric Quartz Transducer for pressure testing of centerfire pistol and revolver, centerfire rifle, and rimfire cartridges. The primary source of the conformal transducers is the US company PCB Piezotronics. The SAAMI pressure testing protocol uses test barrels that have a hole located in the chamber at a location specific to the cartridge. The SAAMI conformal transducer is fitted into a hole that penetrates the test barrel chamber in such a way that the transducer's face, precision machined to match curvature of the chamber wall at the mounting location a specific distance from the breech face, functions as part of the chamber wall. When the cartridge is fired the gas pressure causes the cartridge case to expand, contacting the chamber walls. The portion of the cartridge case in contact with the face of the conformal transducer exerts a pressure on the transducer which in turn generates a minute electronic impulse that is amplified and results in a reading in pounds per square inch (psi). The SAAMI conformal transducer has the benefit of not requiring a drilled cartridge case and the corresponding challenges of inserting and alignment required of drilled cartridge case. Instead it requires a simple pressure test of a sample case from the lot of cartridge cases being used in the test ammunition. This pressure test determines the gas pressure required to cause the case to expand and come in contact with the face of the conformal transducer upon firing. This measurement is referred to as the "offset" and makes allowance for the "loss" of that gas pressure prior to the cartridge case coming in contact with the transducer and generating the impulse. The offset is added to the pressure reading to arrive at the peak pressure reading. Other benefits of the SAAMI conformal transducer are: very adaptive to the high volume quality control testing demands of commercial and law enforcement ammunition production; protection of the transducer from direct exposure to the high temperature combustion gases and hence a comparatively long service life; 80,000 psi (551.6 MPa) maximum working pressure. Cartridges with the same chamber wall diameter at the mounting point of the transducer and which operate within specific chamber pressure limits may use the same transducer interchangeably reducing instrumentation costs.
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Nobody seems to want to explain which is the more accurate method? The truth is unless someone has a very accurate measuring plane and a measurement setup you really don't have a clue what the actual chamber pressure is in any given rifle with any given ammunition. There are likely a dozen outside variables controlling chamber pressure. To argue it simply becomes a moot point.

Ron
 
My dad knew a few things about guns and ammo (worked at APG for years)
And he used the two different cartridges interchangeably.

He likened it to differences in means of measuring.

I myself know diddly squat, but that's how I understand it, and I lose no sleep over it.

Academically speaking, I'm sure there is a difference.
But real world experience hasn't proven it to be dangerous or even hardly worth the debate
 
Made up my mind and not telling

Lotta info given, especially with the colorful A-Blast introduction by Reloadron, to make up your mind with if you want to… or not.

Thanks to everyone who took the time to supply the references and to those who objectively offered opinions….. Doc
 
My TC Venture .223 has a chamber so tight I can't even get the bolt closed on some factory .223 rounds---not taking any chances with 5.56 ammo.

No big deal---my AR will eat the oversize rounds like candy.
 
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