whats the difference .223 vs 5.56 ?


August 21, 2009, 01:07 AM
What is the difference between .223 and 5.56 caliber ammo :confused:
I did not know there was difference . I was looking at a group buy thread and a guy selling 5.56 ammo told another member if his AR was a .223 that it would not be good to shoot the 5.56mm through it .

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August 21, 2009, 01:09 AM
i dont believe there is anything different. 5.56 is the military designation and .223 is the civillian

August 21, 2009, 01:24 AM
I agree, some claim the 5.56 case is thicker and creates more chamber pressure but if that was true a 223 load in a 5.56 case would also create a higher chamber pressure. Also I have never seen proof of a damaged rifle or injured shooter from firing 5.56 in a rifle chambered in 223.

August 21, 2009, 04:25 AM
As a reloader, the distinction is virtually zero. You're going to inspect your own chamber for dimensions to determine headspace, and the distance from bolt face to rifling lands for your max cartridge OAL. You're going to prep and match your own brass. You're going to select your own components and loads from published manuals. So the distinction is Zero for the reloader.

But beware of surplus military loads designated 5.56mm, which are generally higher pressure than commercial standards for 223 Remington and may be loaded too long to fit a short commercial chamber (no guarantee of either, because different military contracts around the world have different specifications). If your rifle can't handle hotter loads or longer loads, you may have trouble putting 5.56mm in that rifle.

August 21, 2009, 06:47 AM
Just the spelling for all practical purposes. :)

Steve in PA
August 21, 2009, 12:49 PM
5.56 chamber has a longer throat to handle bigger/heavier bullets.

Simply put, a 5.56 chambered rifle will shoot both 5.56 and .223 calibers.

A .223 chambered rifle will shoot .223 and "may" shoot 5.56, depending on the bullet.

Steve C
August 21, 2009, 01:07 PM
metric vrs english. Case dimensions are identical. How the military chambers its rifles has no bearing on the cartridge, only on the degree of reliability demanded by military conditions.

Military cases have been known to be thicker than some civilian sporting ammunition cases. As with anything in reloading, data must be worked up for specific components if loading to maximum velocity and accuracy.

August 21, 2009, 01:56 PM
Steve has it pretty correct, but also, some 5.56 designated cartridges may not chamber in tight chambered .223's regardless of bullet length because the 5.56 designated stuff may have a larger case because the tolerance specs for the NATO 5.56 are slightly more open. Obviously, regarding the numbers of caliber designation, it is simply metric vs inch terminology.

Steve in PA
August 21, 2009, 04:32 PM
The ammo-oracle used to have a picture showing the difference between .223 and 5.56mm.

August 21, 2009, 04:43 PM
Read this. http://www.6mmbr.com/223Rem.html Factory Nato/Military ammo in 5.56mm should not be shot in a 223 Remington chamber, see SAAMI website. SAAMI " 5.56MM Ammo Unsafe In 223Rem" Factory Military Ammo
Some Military factory ammo in 5.56mm maybe loaded to higher pressures than 223 Rem factory ammo. When reloading just work up a load using the same components, brass, primer, bullets, powder lot number. Stay away for the maximum charge. http://www.saami.org/Unsafe_Combinations.cfm

August 21, 2009, 04:53 PM
You can show me all your black and white data and fancy calculations but until I see a gun or shooter damaged by firing 5.56 in a 223 chamber I am a non-believer.

August 21, 2009, 05:37 PM
In France, rifles that shoot "military" ammo , can not be bought by the public.

Even a Lebel 1886, i'snt available ........... but magnums (of any calibre) would be OK;

So the .223 (civilian) is an important distinction, between to two rounds.

Ben Shepherd
August 21, 2009, 05:46 PM
There IS a difference in both chamber dimension and pressures! There is even an "in-between" chambering called a "Wylde" chamber(google it) that will usually handle both.

Somewhere on my home computer I've got a drawing that shows both 223 and 5.56 chambers. I'll post a link to it later tonight when I get home.

August 21, 2009, 05:51 PM
I believe you on all the different pressures and all but I still ask show me a damaged 223 rifle from firing a 5.56. I am not saying it cannot happen I am saying there is no proof that it has happened.

August 21, 2009, 06:02 PM
In France, rifles that shoot "military" ammo , can not be bought by the public.

that's not true.

August 21, 2009, 06:14 PM
I am saying there is no proof that it has happened.Actually it has happened, about 40 years ago.

There were some problems with some SAKO Vixen .223 rifles that had tight bores.
There were some problems with Remington 40X .223 target rifles that had very tight match chambers.

In both cases, they were also short throated for the lighter bullets used at the time..

There was no gun damage. Only blown primers.

I think there is still a possibility of a problem with custom chambered .223 rifles.

I also think that all the manufactures making .223 rifles today long throat them to preclude any possibility of a problem with 5.56 ammo in them.

Maybe if you ordered a Remington 40X bench-rest rifle from the custom shop, it might be cause for caution.
Otherwise, I too think it is a non-issue in off-the-shelf .223 rifles being made today. I know for a fact it is a non-issue with my CZ-527 and LC M193 GI stuff.


August 21, 2009, 06:19 PM
Thanks, RC I always value your experiences and posts in the Reloading section here.

August 21, 2009, 09:02 PM
http://www.ar15barrels.com/data/223-556.pdf More than you need to know , or want to. :)

Ranger J
August 22, 2009, 09:58 AM
The only possible difference I have noticed is that it seems some military brass may have slightly less powder capacity compared to commercial brass. I have noticed that my standard load seems to fill the case more than the same load in commercial brass. Whether it is true or not I have read that military brass is slightly thicker so that it can be fired in full auto weapons.


Ben Shepherd
August 22, 2009, 10:06 AM
I believe you on all the different pressures and all but I still ask show me a damaged 223 rifle from firing a 5.56.

Damaged, no. But the few times I've fired true military 5.56 in my contender super 14 barrel, recoil was substantially heavier, I had to get a bit energetic to get the thing back open, and had to use a rod down the muzzle to get the case out.......

August 22, 2009, 10:34 AM
Have a look at this thread I had a major failure with a new rifle with 209 Federal Factory M193 rounds. http://castboolits.gunloads.com/showthread.php?t=60469

August 22, 2009, 02:13 PM
:banghead: Some of these replies are just plain scary!! For reloading purposes, a .223 will hold a bigger charge because it is thinner walled then a 5.56. In a rifle round, a .223 is designed for a maximum of 55000psi at detonation, a 5.56 is designed for 75000psi. SO, if you shoot 5.56 in your .223 chamber you are risking it blowing up in your face because the chamber is only designed for a max of the 55k psi. :cuss: DO NOT shoot 5.56 ammo in a .223, eventually, it may just make you pay for the mistake!!

August 22, 2009, 02:55 PM
I don't know where you got your pressure information, or you rifle strength information, but they are both wrong.

The action strength and chamber wall thickness on a modern .223 chambered rifle are exactly the same as they are on the same rifle chambered in 5.56mm.
No difference atall.

No current commercial or military rifle cartridge is rated at 75,000 PSI, period.

The .223 Remington is rated by SAAMI at 55,000.
The M193 5.56 is rated by the military at 52,000 average, with a SD allowed of up to 58,000.
The M885 ball load is rated at 55,000 with a SD of up to 62,366.

But regardless of all that, SAAMI measures commercial load pressure differently then the military measures military ammo, so there is no exact way to compare the two.

The only 5.56 NATO load even close to 75,000 is the M197 Proof Load cartridge which is rated at 70,000 with a +/- allowance of 3,000.

.223 Remington Proof Loads would be about the same pressure.

According to the official NATO proofing guidelines the 5.56x45mm NATO case can handle up to 430 MPa (62,367 psi) piezo service pressure. In NATO regulated organizations every rifle cartridge combo has to be proofed at 125% of this maximum pressure to certify for service issue. This is equal to the C.I.P. maximum pressure guideline for the .223 Remington cartridge, that is the 5.56x45mm NATO parent cartridge.

I will concede that GI ammo is sometimes loaded a little hotter then some commercial. But sometimes, it isn't.
I will disagree that all 5.56 cases have less capacity then all commercial .223 cases.

I have a few thousand rounds of Remington commercial and LC GI brass in the basement that proves that not always true.


August 22, 2009, 03:10 PM
This is an informative thread for me, given that
I'm about to wander into the world of .223/5.56. (See sig line.)

I'm really excited about it, too. Could lead eventually to getting a .223 bolt rifle,
as well (yikes, did I really write that?! :eek: ), so best to know these things about ammo.

Good to see cool heads prevailing in here. :cool:


August 22, 2009, 10:39 PM
For what it's worth...


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