.223 vers 5.56 Nato Educate me

[6bg6ga]

Was in the gun shop yesterday and overheard a conversation where the counter person was telling a customer that .223 couldn't be used in a gun chambered for 5.56 nato. I don't know for sure but was always under the impression that the 5.56 nato was a higher pressure round and would blow up a .223 chamber. Using this assumption I figured the .223 could be shot in a 5.56 but not vice versa.

As a person on this board that is probably the only one that doesn't own a AR15 or similar I am wondering what you have to say on this subject.

[Bloodman14]

The 5.56 NATO is the military version (higher power) of the .223 Remington. As I understand it, you can fire a .223 in a 5.56 chamber safely, as the .223 is a lower pressure round. Please note, I am NOT an authority on the 5.56/.223 cartridge. That is all I have for you, bud.

[6bg6ga]

Are AR15 barrels stamped 5.56?

[blaser.306]

I think this is where the "wylde" chamber came about! Not posative but from what little I know about it you can safely shoot both designations in them? And AR BBL's are marked 5.56 nato south of the border! The US will not allow any firarms marked with military / nato caliber designations on them to be exported? So our Colt's , Bushmasters Etc. are all marked .223??? I guess it is intended to keep both you and I safer when we sleep at night.

[JSnover]

Post this question on the Military Surplus forum, I know I've seen it before. I think the biggest concern is accelerated wear but I'm not an authority.

[JSnover]

They are interchangeable but you might find some issues with tight chambers, actions may not cycle, stuff like that.

[CastingFool]

From what I understand, the biggest issue is how the ammo is tested for pressure. Here is a report found in Wikepedia.

223 Remington versus 5.56 mm NATO[edit]





These 5.56x45mm NATO cartridges are identical in appearance to .223 Remington. They are, however, not completely interchangeable.
While the 5.56mm NATO and .223 Remington cartridges and chamberings are very similar, they are not identical.[8]

The NATO specification allows a higher chamber pressure. NATO EPVAT test barrels made for 5.56mm NATO measure chamber pressure at the case mouth, as opposed to the location used by the United States civil standards organization SAAMI. The piezoelectric sensors or transducers NATO and SAAMI use to conduct the actual pressure measurements also differ. This difference in measurement method accounts for upwards of 137.9 megapascals (20,000 psi) difference in pressure measurements. This means the NATO EPVAT maximum service pressure of 430 megapascals (62,000 psi) for 5.56mm NATO, is reduced by SAAMI to 379.21 megapascals (55,000 psi) for .223 Remington.[7] In contrast to SAAMI, the other main civil standards organization C.I.P. defines the maximum service and proof test pressures of the .223 Remington cartridge equal to the 5.56mm NATO.

The 5.56mm NATO chambering, known as a NATO or mil-spec chamber, has a longer leade (also referred to as the throat), which is the distance between the mouth of the cartridge and the point at which the rifling engages the bullet. The .223 Remington chambering, known as SAAMI chamber, is allowed to have a shorter leade, and is only required to be proof tested to the lower SAAMI chamber pressure. To address these issues, various proprietary chambers exist, such as the Wylde chamber (Bill Wylde)[9] or the ArmaLite chamber, which are designed to handle both 5.56mm NATO and .223 Remington equally well. The dimensions and leade of the .223 Remington minimum C.I.P. chamber also differ from the 5.56mm NATO chamber specification.

Using commercial .223 Remington cartridges in a 5.56mm NATO chambered rifle should work reliably, but until recently, it was believed this was less accurate than when fired from a .223 Remington chambered gun due to the longer leade.[10] Although that may have been true in the early 1960s when the two rounds were developed, recent testing has shown that with today's ammunition, rifles chambered in 5.56mm can also fire .223 ammunition every bit as accurately as rifles chambered in .223 Remington, and the 5.56mm chamber has the additional advantage of being able to safely fire both calibers.[11] Using 5.56mm NATO mil-spec cartridges (such as the M855) in a .223 Remington chambered rifle can lead to excessive wear and stress on the rifle and even be unsafe, and the SAAMI recommends against the practice.[12][13] Some commercial rifles marked as ".223 Remington" are in fact suited for 5.56mm NATO, such as many commercial AR-15 variants and the Ruger Mini-14, but the manufacturer should always be consulted to verify that this is acceptable before attempting it, and signs of excessive pressure (such as flattening or gas staining of the primers) should be looked for in the initial testing with 5.56mm NATO ammunition.[14]

[GRUMPA]

Here's a rather detailed link explaining it.

http://www.gundigest.com/223-vs-5-56

[JSnover]

I can't remember the source. Years ago someone summed it up for me: MilSpec rifles are best with MilSpec ammo. It may not be cast in stone but it does simplify things.

[Multigunner]

Some milspec 5.56 ammo may be too fat in the neck for some .223 chambers.

[Wayne S]

The case dimensions for factory loaded 223 & Nato ammo are the same, BUT look at the chamber Dem.,especially in the neck and throat area. The NATO chambers are a little on the "loose" side,which is to be expected for something meant for battle field conditions.
http://castboolits.gunloads.com/showthread.php?223721-223-Wylde-and-223-NATO-Dem
One of the on line loading data sites, I think it's "Ram Shot" lists both 223 & 5.56 NATO. The 223 data loads to ( + - ) 55,000 psi, where as the NATO data goes to ( + - ) 62,000

[Uncle R.]

Was in the gun shop yesterday and overheard a conversation where the counter person was telling a customer that .223 couldn't be used in a gun chambered for 5.56 nato.

Another gun shop ex-spurt.
Cheez...
<
Uncle R.

[Larry Gibson]

Having actually pressure tested a lot of different lots of 5.56 NATO (M193 and M855) and different makes and bullets weights of commercial .223 Remington in both milspec 5.56 NATO and .223 Rem chambers the truth is there is little truth to most of what you hear and a lot of what you'll read on this subject. Surprisingly the Wikipedia explanation quoted above comes closest. In reality the only time pressures get higher than spec for any modern actions we see the oft higher pressured 5.56 cartridge chambered in is when the chamber is a short throated .223 chamber is used with the heavier bulleted load of the M855 cartridge. Chamber pressures can get a little high then but I've not measured anything that was outside of the MPSM for the 5.56 cartridge.

There is a caution in the M16A1/M16A2 through current M4 series manuals (FMs) that M855 ammunition should not be used in older M16A1 rifles. Many believe (lots of barracks BS on that one) that it is because the M855 is "higher pressured". However that is not the case and if one bothers to read the manual instead of listening to the BS one finds it is simply because of the 12" twist of the M16A1 barrel which won't properly stabilized the heavier 62 gr bullet of the M855 ammunition. Thus accuracy will be poor if not non existent is the real reason.

If you have a short throated .223 chamber in any modern action then M193 ammunition loaded to milspec will not exceed the psi limits and the rifle will not "blow up". It will shoot just fine, maybe not as accurate because of the lesser quality bullets but the psi will be within the pressure standards for the action. If you have a modern rifle with a 5.56 chamber, with or w/o a "Wilde" throat, then both the heavier bulleted 5.56 (60 + gr) and .223 Remington will be safe to fire in it. The real concern is knowing the rifling twist of the barrel. A 7 - 10" twist barrel will shoot most any bullet weight up to 75 gr accurately. The 12 and 14" twist barrels will shoot bullets up through 55 gr accurately. That applies to jacketed bullets.

The statement regarding "accelerated wear" from higher pressured cartridges applies to all firearms not just those chambered for the 5.56/.223. Use low pressured loads and the barrels last longer and the actions, if semi or full automatic, will wear a lot less. Makes sense but is misconstrued to be damning in this instance of cartridge use in 5.56/.223 chambered rifles, especially ARs.

Larry Gibson

[M-Tecs]

Once again Larry is spot on!!!!!!!!!!

[GabbyM]

Thanks for that one Larry:

http://ar15barrels.com/data/223-556.pdf
Here is a link to different manufactures reamer dimensions. Just to show people how confusing things are with a wide deviation in chamber measurements just between companies manufacturing reamers. Hope we don't overload this guys server account data limit.

NATO chamber has .004" longer head space. Wider at the shoulder and base. With a throat diameter of .2270” instead of .2245” and .025” longer than a SAMI 223. Bill Wylde’s chamber is close to the NATO but with the tighter throat diameter of the 223 SAMI. Still has the length of the NATO for single shot loading the 75 & 80 grain bullets.
Below is a copy paste of a spread sheet. It looses spacing between numbers.
Shows the difference between a 5.56mm and 223 chamber. But remember there are variations in different reamer designs. I typed in the comas trying to make it easier to read. Measurements are in inches.


# Item, 223 Rem, 5.56 NATO, Difference

C Base Diameter, 0.3760, 0.3780, 0.0020
D Shoulder Diameter, 0.3553, 0.3560, 0.0007
F Neck-2/Case Mouth, 0.2540, 0.2550, 0.0010
G Freebore Diameter, 0.2245, 0.2270, 0.0025
K Base-to-Case Mouth, 1.7720, 1.7750, 0.0030
L Base-to-Shoulder, 1.2340, 1.2380, 0.0040
M Neck Length, 0.2200, 0.2180, -0.0020
N Freebore Length, 0.0250, 0.0500, 0.0250
R Throat Angle (Degrees), 3.1, 2.5, -0.6

[lefty o]

not all AR barrels are marked or chambered as 5.56, there are some that come from the factory marked and chambered .223 .

[GabbyM]

not all AR barrels are marked or chambered as 5.56, there are some that come from the factory marked and chambered .223 .

Correct.
I have one. DPMS 20 inch bull barrel in 223 with 1-9” twist rate. Makes a ten pound gun empty. Nice tight chamber. Actually had to purchase a new FL size die to get surplus brass sized down small enough to chamber. Not a small base die. Just the RCBS die I’d been using for thirty years on cases fired in my NATO chambered rifle had worn some. I keep that die for the 5.56mm stuff. I just minimum FL size my NATO brass. If you set the shoulder all the way back to regain that extra .004” of head space you have to trim brass every time , or at least I do. RCBS X die is supposed to be the solution to this stretching. I own three rifles in 223 and 5.56mm. They all have there own target ammo.

[GabbyM]

Some milspec 5.56 ammo may be too fat in the neck for some .223 chambers.

I have some Winchester white box here that won't chamber in my NATO 5.56mm. They bulged the neck with there crimp die. Would fail milspec QC. Which I'm sure it did before Win dumped it on the civilian market as M-193 ball. There is for sure a lot of junk on the market.

[PalmettoShooter]

ive always heard 223 is okay in a 5.56, but 5.56 in a 223 is not ideal. it wont always cause problems, but its just not the way you want to do things. this is not an expert opinion from me nor do i know what i am talking about (especially if you ask my ex). the wylde chamber is the middle ground to this and is made to take both.

[6bg6ga]

Here's a rather detailed link explaining it.

http://www.gundigest.com/223-vs-5-56

Just finished reading this and its great. I think everyone would enjoy reading this detailed bit of history.

[6bg6ga]

This is probably going to be a short thread but possibly one that should be made a sticky because the posts are informative and spot on. Anyone after reading this thread can go out and purchase the correct rifle and know the proper ammunition to use in it and why.

Thanks guys..

[6bg6ga]

Did some looking on some AR15 parts sites and found that 95% or more of them have barrels that are marked 5.56 Nato. So I guess if it says 5.56 on the barrel its safe for 5.56 and 223 and if it says .223 then one might be advised not to use the 5.56 round.

[Gunnut 45/454]

I don't know you tell me if you see the difference? I see it. Can you? Here's a hint- what would happen when you shove the case mouth into the lead on a rifle? Or engage the bullet into the rifling? As been mentioned here already - .223 Rem chambers have shorter leads/tighter chambers! An 5.56mm is loaded hotter then .223 Rem. An SAMMI warns against shooting 5.56mm in which chamber?