.223 cal vs. 5.56mm

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Good for them.

Not every AR marked ".223" actually has a .223 chamber. Some chamber 5.56 but mark .223. You can take the chance, I won't.
 
I don't base what I say on nothing.

December 4, 2002

TECHNICAL NOTE 45: 5.56 NATO vs SAAMI .223 REMINGTON CHAMBERS

BACKGROUND: We are often asked whether our rifles feature NATO (North Atlantic Treaty Organization) or SAAMI (Small Arms and Ammunition Manufacturers Institute) standard chambers, and whether it makes any difference.

FACTS:

.223 Remington (SAAMI standard) and 5.56mm (NATO standard) rifle chambers are almost identical. The difference is largely limited to the “freebore,” the cylindrical space in front of the case mouth, and the “lead” or “leade,” the the tapered region that eases the bullet into full engagement with the rifling. NATO and SAAMI cartridges can normally be used interchangeably with no problem.

The SAAMI chamber features less freebore and a tighter leade, which normally provide better bullet fit and match-grade accuracy than the NATO chamber. It is wonderfully suited to match bullets.

Millions of rounds of NATO ammunition have been fired safely in Eagle Arms' and ArmaLite’s SAAMI chambers over the past 15 years. Occasionally a non-standard round (of generally imported) ammunition will fit too tightly in the leade, and resistance to early bullet movement can cause elevated chamber pressures. These pressures are revealed by overly flattened or powder stains that reveal gasses leaking around the primer.

The first few rounds of ALL ammunition, from whatever source or lot, should be checked for pressure and other signs of defect before firing large quantities. If you have a problem, you can generally bet that the ammunition meets neither SAAMI nor NATO specifications.

ArmaLite has adopted a practice of using a special, modified SAAMI chambers in its stainless steel match barrels. This chamber is better for match use than the NATO chamber, but fires the NATO ammunition perfectly. We use the NATO chamber in all moly (phosphated) and chrome-lined barrels.

ArmaLite’s larger AR-10® rifles are all chambered with 7.62mm NATO chambers. .308 Winchester (SAAMI standard) ammunition functions perfectly in the 7.62mm chambers.



© 2001 ArmaLite, Inc®.
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Basically, if the ammunition and your chamber are within their respective specifications, there should be no interchangeability issues. Also, it wouldn't surprise me if you were to examine several samples of .223 and 5.56 chambers, you would find that there was more variance between samples from the same set of specifications than between sets, due to manufacturing processes and accepted tolerances.
 
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I've got to admit I fired a lot of surplus ammo out of my .223 Remington 700. I never had any issues at all but that's one person and one gun.
 
Been down this road a few times but I'll travel it again. You can shoot .223 through your 5.56 but your accuracy is gonna suffer it. DO NOT SHOOT 5.56 IN YOUR .223!!! 5.56 is a NATO round designed for military specs. Its loaded at a much high pressure than .223 & though it may or may not KA-BOOM your rifle, it very likely will damage it.

I shoot .223 through my 5.56 chambered AR. Never had any issues. I won't shoot 5.56 in my .223 bolt guns though. Why chance it? When or if in doubt, just run what the weapon chambered for.
 
Good share of .223 guns are made to shoot 5.56 and have a 5.56 chamber. I would not worry about it unless is a match chamber .223.
 
leadcounsel

If you want mass confusion in an open forum ask about the .308/7.62 NATO or the .223/5.56. If you do your research and sift through the garbage while studying the subject looking for "FACTUAL" information you will find the following:

1. CIP the European equivalent of the American SAAMI considers the .308/7.62 and the .223/5.56 the "SAME" cartridge.

2. Military chamber pressure readings are taken at the neck of the cartridge and American SAAMI chamber pressure readings are taken at the mid point of the cartridge body. Military pressures read higher than SAAMI pressure readings "BUT" they are one in the same actual chamber pressure. (example, 60 mph = 100 kph and both are the same actual speed)

3. The only difference between the two rounds is the M16/A4 "now" has a longer throat to accept the heavier and longer military bullets. The older and some of the newer .223 have a "shorter" throat and slower twist rate of 1 in 14 twist. My new .223 has a longer throat with a 1 in 9 twist and the manual states it can safely shoot either type ammunition. If you shoot the newer 5.56 military ammunition in rifles with a 1 in 14/1 in 12 twist the shorter throat will cause pressure spikes when shooting the "longer" and "heavier" military bullets. (pressure spikes, chamber pressures that are higher and peak sooner than normal)

Below, .223 and 5.56 throat differences
(short throat = light shorter bullets, long throat = heavy longer bullets)

556natochamberversus223remingtonchamber02.gif

Below, eight variations in .223/5.56 camber types and throating for the "SAME" cartridge.

223reamers-1.gif

The .223 cartridge and the 5.56 cartridge for a practical purposes are the same, the difference is "some" .223 rifles were designed were to shoot shorter and lighter bullets and the "military" keeps changing bullet types to get the M16 to hit harder and have more knock down power.

NOTE: Before I bought my heavy barrel .223 Stevens 200 I knew it had a longer throat and a 1 in 9 twist and I would be able to shoot both types of ammo without ANY problem.

Below, two of my "civilian" :rolleyes: rifles that can shoot "military" ammunition, .223 Stevens 200 and a Remington 700 30-06.(and I still have both my eyes and all my fingers and both rifles are in one piece) :eek:

IMGP7358.gif

Five gallon buckets of .223 and 5.56 cartridge cases waiting to be reloaded next to my reloading bench. ;)

IMGP6526.gif
 
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Another neat deal is 5.56 and .223 brass pretty much weight the same too so you dont have to worry about cutting back loads like you do with GI .30 cal brass vs commerical brass.
 
And to add to the confusion, many chambers marked .223 aren't cut to .223 SAAMI specs; just as many chambers marked 5.56mm aren't cut to 5.56mm NATO specs. Many manufacturers use a hybrid chamber knowing that their customers may be shooting a wide variety of ammo but will still expect high levels of accuracy.

If you get something like a Michiguns 5.56 gauge and start actually measuring random AR chambers, you'll be shocked at how few are actually cut as 5.56 chambers, markings or not.

Having said that, the worst I've seen happen by firing 5.56 NATO ammo in a short-leade .223-ish chamber is that the gun will pop primers/fail to cycle properly. No kabooms, parts breakage or anything dramatic.
 
Generally, the only issues you're likely to run into are well stated in the Armalite quote above. If you're concerned regarding your ammo - at the range - allow a full round to be seated without assistance (rifle action only) into the chamber and extract it to view the areas of the ogive for signs of contact with the lands of the rifling. To be a little more particular, dip the projectile in layout fluid or simply black it with a sharpie.
 
Bigedp51, the brass for .223 and 5.56 are the same. .223 and 5.56 are chamber nomenclature and specifications, not brass. 5.56 NATO ammunition is also loaded with a pressure measurement taken at the case mouth whereas SAAMI .223 is taken at the chamber. Two very different measurements and they are not interchangeable.
 
RhinoDefense

1. I said NOTHING about brass.

2. If the SAAMI measures chamber pressure for a military cartridge and gets "X" for a pressure reading and the military measures pressure using EPVAT method for the same cartridge and gets "Y" for a reading, then "X" and "Y" equal the same pressure. And I did NOT say the EPVAT and SAAMI pressure taking measurements were the same, do NOT put words in my mouth and try and read what a person writes more carefully. ;)

Example below, between CUP and PSI pressures for the .308 and 7.62 NATO. (done with a little humor) :rolleyes:

As you can see below it is safe to put 32 PSI in your tires BUT if you put 220 kPa in your tires they will blow up and kill everyone in a 300 yard radius. :eek:


IMGP3024-1.gif
 
I think this would make a good Mythbusters topic. along with the 308/7.62 nonsense. Anyone else want to join me in sending the topic to them? It appears you need to join that forum to suggest it, but I think if we make it a hot topic they would pay attention.
 
The 5.56 has a higher pressure rating than the .223 but I have yet to see any difference in shooting 5.56 loads out of the load manuals in a .223, They always list heavy bullets in 5.56 pages and light bullets in .223. I shoot 75 gr A-Max bullets in my Savage .223 and they have shot well for about 6000 rounds.
 
RhinoDefense said:
Bigedp51, the brass for .223 and 5.56 are the same. .223 and 5.56 are chamber nomenclature and specifications, not brass. 5.56 NATO ammunition is also loaded with a pressure measurement taken at the case mouth whereas SAAMI .223 is taken at the chamber. Two very different measurements and they are not interchangeable.
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The two pressure readings are different because they are taken from different places. This has no bearing on compatibility. What would concern you is the chamber specifications, which are virtually identical, except for increased freebore in NATO spec chambers, which is to accommodate the heavier bullets used in NATO ammunition.
 
Ar180shooter said:
Lots of people have shot 5.56 out of their .223 marked AR's over the years without any ill effects.
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And NASA flew for years with foam on the tanks without any ill effects.

While the rounds are nearly identical in size, the pressure specs are different.

A 5.56 barrel has to be able to handle 62,366 PSI while a .223 only has to be able to hold max. pressure of 55,000 PSI.

Is that 7k difference going to matter? Most likely not unless there was already some type of defect in the barrel or just a poorly made barrel. But I'm not shooting rounds that can develop more pressure than what the gun was designed for and a .223 was designed for less pressure than a 5.56 can develop.
 
From what I understand there are some very slight differences in .223 and 5.56. My Mini-14 shoots both with 5.56 having a touch more recoil.

I personally think that the AR guys use 5.56 because 5.56 sounds cooler to them .223.
 
I'm still waiting for the report of an actual safety issue from shooting 5.56 in .223 chamber or vice-versa.

I'll retire from the referral fee to the lawyer who gets the slam dunk product liability case.

See AR180Shooter's post near the top of this tread. Guess this will never be put to rest.
 
I have 3 223 and I have shot thousand's of 223 and 5.56 and never had any trouble with them. I also reload for them and had never had any trouble with them. My buddy goes out west to shoot Peria dogs every year and he takes 3 223 and 8000 rounds for them.
 
That's ridiculous. Picking a calibre based on how "cool" it sounds.

We tend to use 5.56 because of all the confusion apparent on here --if it is okay to use .223 in 5.56 but not the other way around, and you can't get clarity on the issue, then just go with the safest bet. It would be like if the same argument existed over .357 and .38, why take the chance? Just get a .357 and be done with it. Because our loadings are limited by magazine length, the exotic chamberings and extra leade do little to sway the argument one way or the other for the AR crowd.

Finally, when in doubt, just match the number on the headstamp or box to the number on the barrel and problem solved. This should have been included in your basic firearms knowledge package you got way back when. Use all others at your own risk.
 
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