223 Load Data vs 556

[jmr40]

Either round will chamber and fire interchangeably, the biggest difference is a more generous throat in 5.56 chambers. This aids reliability in military rifles.

5.56 CAN be loaded to SLIGHTLY higher pressure than 223. But I seriously doubt that any commercially loaded ammo is going to be loaded right to the max. It is highly doubtful that you'll ever find 5.56 ammo that actually exceeds 223 pressure limits. If you handload and like to push the envelope maybe.

If your rifle has a 5.56 chamber either cartridge works fine. There is the potential of being overpressure if 5.56 is loaded in a 223 chamber. A bolt rifle is strong enough to easily handle this.

In the real world the only concern is that 5.56 fired in a semi-auto with a 223 chamber might not function reliably and long-term use could damage the gun. When was the last time you saw a semi-auto chambered in 223? The only one I'm aware of is the very early Ruger Mini-14's. Ruger quickly changed that so Mini owners didn't damage their rifles shooting surplus 5.56.

Just for perspective, there is a far greater difference in pressures, and even chamber dimensions between 30-06 rifles and ammo made in the last 100+ years. The 30-06 ammo my grandfather carried in WW-1 was a 150 gr bullet at 2700 fps. The ammo my father carried in WW-2 was a 150 gr bullet at 2800 fps. A typical modern factory load is a 150 gr bullet at 2900-3000 fps and there are some specialty loads as fast as 3100 fps. That's a wide range.

Most any 30-06 bolt rifle will handle any of those loads, but you do sometimes see enough difference in manufacturing tolerances to find some loads that cause problems in some rifles.

The Garand however was designed around the 2800 fps load. I've never heard of it causing a dangerous situation, but hotter loads will damage the rifle, and those loads are not recommended for other commercial semi-auto's in 30-06.

 

[MarkCO]

Is -- or is not -- 5.56 NATO pressure significantly different than 223Rem...

- When fired in a compatible chamber ?
- When measured in a similar manner ?

Yes, and yes. Any ballistician will tell you that. But to jmr40's point, you won't find any .223 Rem loaded to 55Kpsi from the factory. You will find 5.56 ammo loaded past 55Kpsi (measured the same way, in the same chamber), but none that I am aware of past 60Kpsi. Fire that in a .223 chamber, yes, the pressure will definitely be higher, but well within the factor of safety of any barrel. And yes, I have seen blown out extractors and evidence of excessive pressure on the case from that very thing.

This article accurately explains the differences if anyone wants to read it.

https://ammo.com/comparison/223-vs-556

FWIW, with the .308, the inverse is true. The 7.62x51 NATO round is LOWER pressure than the .308 Winchester cartridge.

 

[Unclenick]

It's close to accurate. He typoed or misread the freebore length difference. It is 0.025", and not 0.125" difference. Several other dimensions are also different. This comparison of Clymer's 223 Rem and 5.56 NATO reamers has a base diameter and shoulder width and other dimensional differences. This comparison shows different reamer makers don't match each other exactly on the 5.56 NATO, but presumably, all are within NATO spec.

What I've read is NATO rejected M193 for adoption because of its failure of a particular penetration test that they considered standard (it may have been something like a 300-meter helmet penetration test, but I've forgotten the details). In any event, the Belgian development of the SS109 was the answer to that, and they did raise the peak pressure average limit by 6% to get the heavier 62-grain penetrator bullet to pass the test.

There's a long article online with actual Pressure Trace Measurements with, IIRC, two 5.56-chambered ARs, and one 223-chambered AR. The same load in all three had the peak pressures for the 5.56 chambers bracketing the 223 chamber pressure, one being higher and one being lower. 6% is getting into the noise range for individual rifle testing.

 

[tangolima]

I pick up brass from the range. Most of them are milsurp 5.56 NATO. A lot of them have cratered primers. I think they have been loaded on the warm side. Occasionally I see pierced primers or even loose primer pockets. I would believe if those rounds were to be fired in .223 Remington chamber worse things could happen. I just haven't seen or read about one yet.

-TL

Sent from my SM-N960U using Tapatalk

 

[mehavey]

Belgian development of the SS109 was the answer to that, and they
did raise the peak pressure average limit by 6% to get the heavier
62-grain penetrator bullet to pass the test.

...[That?] same load in ... 5.56 chambers bracket[ed] the [the] 223 chamber
pressure, ... 6% is getting into the noise range for individual rifle testing.

Did I read that correctly ?

.

 

[Unclenick]

I assume you read it as I intended, but it's all within the limitations of the measuring systems involved. If you look at the U.S. copper crusher numbers, which were the measuring system in primary use when these cartridges were developed, the M196 round is rated at 52,000 psi by U.S. type crusher (52,000 CUP in SAAMI terminology), and it is the same copper crusher number SAAMI adopted for 223 Remington. The U.S.'s NATO ballistic equivalent (four-leaf clover or four-blade ship's propeller symbol in addition to the cross-hairs inside a circle symbol) to the SS109 is the M855 round, and it is rated at 55,000 psi by U.S. crusher instrument.

When you look at the shift to the piezoelectric transducers, M196 and 223 Remington go to 55,000 psi by transducer (also psi in SAAMI terminology), and M855 goes up to about 58,100 psi (this number is in some declassified ammo specs you can find on line). The potentially confusing thing here is the same number magnitude, 55,000, appears both for the M855 crusher value and the M196 transducer value, which is a coincidence.

If you move to the European-style instruments with their slightly differently placed pressure ports and metric piston diameters, their copper crusher puts the original M193/223 Rem pressure 3700 bar (53,664 psi), so you know their system reads higher to start with. I don't have a European transducer number for M193/223 Rem pressure. What I know is that their transducer number for M855/SS109 is 4300 bar (62,366 psi) and that when NATO went to that number, the CIP adopted it for 223 Remington. So if you buy European-made 223 Remington, it is running at the same pressure as SS109, and so is not lower as it is in the U.S. They did the same with 7.62 NATO and 308 Winchester. The European pressure specs are the same for both. I got this confirmed in an email with Sellier & Bellot several years ago. The fellow I was communicating with looked at both their NATO and CIP pressure numbers for both military/commercial cartridge name pairings and confirmed they all match.

Anyway, the pressure differences are much ado about nothing and are not an issue at this point in time. The only exception will be if surplus quantities of the new M855A1 start to be available. It runs a faster powder at a higher pressure than M855 (but I don't have a number) to reduce M4 muzzle flash and has been reported to increase throat erosion significantly.

To clarify my 6% number being lost in the noise, this is when you move around among rifles. In other words, you would need to be using the same pressure test gun for both M196/223 Rem and M855 or SS109 to see the difference clearly.

 

[BandeauRouge]

Alot things have been left out of the factual history of these two cartridges...

When the 5.56x24 was adopted for military usage, they simply took the complete SAAMI drawings for the cartridge, the chamber, and the loading data. It wasnt until we had the change in powder type, bad environment, lack of cleaning, that the US Army altered the chamber throat.

However EVERYONE likes to ignore the following facts..

ONLY the original M193 load is actually the original form of the Nato round, ie genuine .223 remington.

The ONLY M193 load that is genuine is ammunition that was loaded in NATO factories, and almost always needs the nato star on the head stamp.

SAAMI DOES NOT recognize 5.56 NATO as a cartridge, thus any 5.56 NATO ammunition on the store shelf from non military factories, is NOT safe in a .223 chamber.

WHY? As the bullet weight changed 3 times, they increased the chamber pressure read out.. NON NATO factories reloading that nice 10$ box of M193... are allowed to use any of these three pressure levels.

TO put it bluntly, its like purchasing a box of reloaded 38 smith and wesson, and not knowing if it was loaded to the original 38 SW, or to 38 special, 38+p, or 38/44.

But the biggest issue is that BOLT ACTION RIFLES are considered to be cut at the ideal drawing dimensions, and the NATO ammunition to be at the sloppiest dimensions.. and will supposedly choke up in the chamber upon firing in ways .223 wont.

There is an AR forum where i saw several threads by people who were using AR-15 that left the factory as .223 that had been hit with a 5.56 nato finish reamer and were fine after 3 or 4,000 nato rounds.

Also no one thinks about it,,, one cannot claim that the use of 62 grain 5.56 NATO ammo in a .233 is bad because of bullet weight, i can get .223 rem with 62 grain bullets at the same nominal muzzle velocity.

 

[44 AMP]

SAAMI DOES NOT recognize 5.56 NATO as a cartridge, thus any 5.56 NATO ammunition on the store shelf from non military factories, is NOT safe in a .223 chamber.

Lack of SAAMI recognition has NOTHING to do with the physical safety of a load in a given chamber. It just means SAAMI has not tested and approved it.

There are a LOT of things that are physically, mechanically safe that SAAMI has not tested or approved.

 

[Marco Califo]

Another interesting article:
https://www.luckygunner.com/labs/5-56-vs-223/

 

[JohnKSa]

Pretty good article and consistent with the general information available from official sources.

What I take away from it is that he confirms the advised against mismatch can drive pressures higher than SAAMI standard for .223 although not by a large margin. To me, it looks like one can think of 5.56 in a .223 chamber as being similar to firing +P .223 ammo.

I would say it's very unlikely to cause any sort of catastrophic incident (it's not going to blow up guns that are in good condition), but there is the possibility of irritations like popped primers, especially in the presence of other contributing factors such as high ambient heat, etc.

 

[mehavey]

...very unlikely to cause any sort of catastrophic incident....

Concur. Most "likely" worst is primer pockets loosening prematurely upon multiple reloading if 60ksi (using standard measuring techniques) is repeated.

 

[Marco Califo]

IIRC Unclenick has posted that the "pressure differential" was due to different measuring techniques, and military proof readers repeatedly changing correct info to wrong info that looked better to them. I believe this was CUP vs. PSI, and the true absolute pressure differential was minimal (and thus not really a concern).

 

[JohnKSa]

Luckygunner (in the link you posted) did see an absolute difference in the pressure measurements even when they were done using the same techniques.

Which is kind of what we should have expected since solid sources (SAAMI, Winchester, Fulton Armory, Hornady, Remington) have been telling us, for many years, that there was a difference.

The difference is not massive and, by itself, probably won't cause serious issues in a firearm in good working condition--sort of like shooting +P ammo. But your source does show that it results in pressures over SAAMI max. I would expect that sort of pressure rise, particularly in conjunction with additional contributing factors such as high ambient temperatures could possibly cause minor issues (e.g. popped primers).

 

[44 AMP]

I would point out that even with the noted difference the ammo is still well below proof level loads, and while you might encounter things that make the ammo/ammo combination unsuitable, its NOT "unsafe".

Unless your firearm is seriously mechanically /metallurgically flawed its not going to immediately shatter like glass dropped on concrete from a pressure below proof limits.

 

[Unclenick]

Tangolima,

Late in the day, but I found this sheet on go and no-go, and field reject for 5.56. It turns out they vary a bit by weapon system, and the gauges are specific to weapon systems, but that sheet will give you something to stare at, anyway. The fellow posting it says:

Here are headspace gauges specified for the M16/M4 chamber of new production weapons (P/Ns 8443915 and 8443949). There is also a maximum safe headspace gauge (P/N 7799734).

The generous headspace on the largest 5.56 NATO gauge is a reject, change barrel indicator for the armorers. Apparently, the rounds still meet the relatively coarse military accuracy and performance requirements even in a pretty loose chamber.


BandeauRouge,

You've got a bit of confused information, too.

The military did not get the 223 from SAAMI. Its development was started in 1957 for the military by Remington and Fairchild. They already had it by the time Remington submitted the cartridge to SAAMI for commercial standardization in 1962. The military didn't officially adopt the cartridge as M193 for another year, but that was just a change in designation, not a change in design.

M192 is not and never was a NATO round. It was submitted to NATO for evaluation as a potential second NATO small arms rifle round (7.62 NATO being the first) and didn't pass one of the NATO penetration tests. NATO responded by soliciting the development of a version that would pass their test, and that task was given to FN Herstal, who kept the M193 cartridge case as a basis for developing their SS109 round, which raised the bullet weight to 62 grains, added a penetrator, and raised the maximum allowed average pressure by 6%. This is the cartridge that was adopted as the NATO second small arms rifle round in 1980, not M193.

You will find M193 with the NATO circle and cross symbol on it, but this does not mean it is NATO ammo. That the interoperability symbol. It just means NATO small arms designed for 5.56 NATO will operate with it; fire, eject, feed, so it can be used for some kinds of practice or substituted in an emergency. The symbol is there to tell other NATO troops that if an American with M193 hands them some in a pinch, their guns will function with it. Only if ammo also has the NATO four-leaf clover symbol is its ballistic performance a match to NATO ammunition.

 

[JohnKSa]

...while you might encounter things that make the ammo/ammo combination unsuitable, its NOT "unsafe".

Do you mean that: "... it's very unlikely to cause any sort of catastrophic incident (it's not going to blow up guns that are in good condition), but there is the possibility of irritations like popped primers, especially in the presence of other contributing factors such as high ambient heat, etc."?

 

[Unclenick]

I don't actually think even popped primers are an issue. As mentioned before, the CIP standard allows all 223 Remington to be loaded to the same 4300 bar (62,366 psi) that NATO uses as a maximum average peak pressure spec. A tech at Federal told me that works out to a little over 58,000 psi on an American-style conformal transducer. I've found military pressure specs that state a limit of "58,100 psi by transducer," so that seems confirmed.

There are always a couple of things that cause confusion. One is that the different pressure measuring systems don't all read the same cartridges at the same pressure. Another that escapes notice is the maximum average peak pressure is a worst-case average (not a required pressure), and because it is an average, it allows some rounds in a test to go over and some under in meeting that average. How far over? The CIP allows 15% worst case. So an individual round in a ten-round average can be as high as 4945 bar (71,721 psi) and still qualify for the ammo lot. It seems like a lot, but it is still 10% below their 125% proof level. The SAAMI system uses a different approach. It specifies the maximum average pressure and then superimposes the Maximum Extreme Variation (MEV) over top of the MAP. If you calculate the worst case for the ten-shot average they use, then if 9 shots were all exactly 2.04% below MAP and the 10th shot was about 18.3% above MAP, it would still meet the SAAMI MAP. The odds of that happening exactly that way are teensy, but the theoretical possibility is there.

In practice, as MarkCO said, it's pretty unusual for a lot of ammo to actually reach the MAP, much less go over.

 

[JohnKSa]

Did you read the Luckygunner article? It confirms what the ammo companies and others have been telling us for many years. Namely that 5.56 in a .223 chamber, gives higher pressures than .223, even when measured the same way. In fact, they showed that the pressures could (and did) exceed SAAMI max in some cases. In one test, virtually every round was over SAAMI max pressure.


https://www.luckygunner.com/labs/5-56-vs-223/

I know. He must be in on the conspiracy too. I just wish I could figure out why so many organizations and experts have decided to try to mislead the shooting community on this topic...

 

[HiBC]

Here is what jumps out to me (You may disagree) .

There was the .222 and .222 Magnum. Both were mostly Varmint/ target cartridges.. Folks (and Marketing) mostly wanted High Velocity,which leans toward light bullets. Twist rates were established by light bullets.

Along comes the AR-15/M-16. The . 223 round was born. This happened before the M-16 was adopted or there was a 5.56 Nato.

Early AR-15's were .223. Twists and bullet weights (and probably chambers) were standard .223. Once again,there was no 5.56 NATO, yet.

Lessons were learned,the Military needed a little something different.
Bullet weight,twist,and chamber details evolved to meet military needs.

And even the .308 went metric for NATO. It was its own 7.62 NATO. I don't know, but it MAY have had some different specs than the.308 Winchester loaded for your Model 100 Deer Rifle.

No matter. It was optimized for the M-14 and M-60.

You could buy .308 at Walmart. Handloaders adjusted for case volume.

Then AR/15/M-16 match shooters started using heavy bullets for longer ranges. And Yes,the 62 gr NATO became a standard.

69, 75, and 77 gr loads became a standard for 600 yd shooting . Even 90 gr bullets were single loaded. Yes,we have Wylde .223 and military 5.56NATO chambers tailored to heavier bullets and barrels twisted appropriately.

And folks load 600 yd loads rather zippy sometimes. Some accept the primer pockets will be loose. They leave the brass at the range.

The brass scrounger reloader finds it,and jumps to conclusions,

If you have a Rem 700 factory chambered for 223 Rem, it likely won't be twisted tight enough for 77 gr bullets. Why would you want a chamber throated for heavy bullets? You might want a chamber for 52 gr Match Kings or 45 gr Varmint Dusters.

Most folks want their AR's and etc chambered for Wylde or 5,56 Nato with 1 in 7,8 or 9 twist.

Aside from the different measurement systems and various "customer needs"

the topic is ,IMO,an over beaten dead horse.

If we list all the different .223 and 5.56 brass, from LC to WW to Rem To Lapua to PMC to Fiocchi to PMC and S+B. then Barnes solid copper bullets vesus Sierra Cup and cores, Remington Bench Rest primers vs CCI mil spec...

And powder shortages causing people to ask "Can I shoot up this Varget behind 55 gr FMJ bullets? Or this 4064, or (shudder) this Blue Dot?
How high on the list of worry should 223 vs 5.56 be?


Yes! Those who love to argue the pont still want to get their thongs in a knot over 223 vs 5.56!!
The horse is dead! Give it a break!

If your rifle is chambered .223, load for targets or prairie dogs or whatever with bullets of a weight for your rifling twist. If the bullet matches the twist,
likely the throat will match the bullet.
77 gr bullets will not shoot well out of a 1 in12 or 1 in 10 twist.They may be inappropriate for a .223 Rem chamber throat.

Its not that hard.

 

[44 AMP]

Early AR-15's were .223.

Actually, the earliest AR-15s were .222 Rem.

The story, as I've heard it (may or may not be entirely correct) is that at the time, the USAF got their small arms and support (parts, etc) from the Army. They had been using M1 carbines, and the Army was going to drop them.

Gen LeMay needed a new weapon for his SAC guards and general airbase security, and the M1 carbine was going away. He was introduced to Stoner and his new AR design, and thought it would be good for what he needed. LeMay showed it to JFK and he approved.

Then the "whiz kids" of the MacNamara defense dept decided it would be the new standard infantry rifle. Lots of people in the Army objected, and some of them set requirements the .222 could not meet, hoping this would kill the idea. The .222Rem Mag could, but it was just a bit too long to work in the AR action, and the .223/5.56mm round was the result. It met the performance requirements, and fit into the AR action.

There was still a faction that opposed the gun and its cartridge, and they did what they could to discredit it, changes in rifling and powder specs etc. End result, some GIs died and we kept the M16 anyway. Sad story, but ancient history now.

This was long before NATO got involved. Lots of things have happened since then and we have a lot of possible chamber, twist bullet and cartridge to choose from and mix together. some of them don't play nice with each other, but none of them destroys rifles.