.223 remington versus 5.56 x 45 mm NATO - is it safe to interchange???

Ar180shooter said:
Sure!

:) = good
:( = bad

7.62 round in 7.62 chamber :)
.308 round in 7.62 chamber :)
.308 round in .308 chamber :)
7.62 round in .308 chamber :( - Again, your #### probably won't fall off, but when dealing with firearms, it's better to be safe than ####-less!

AFAIK, the 5.56 vs .223 and 7.62 vs .308 debates are essentially identical. Shooting a 7.62 cartridge in a .308 chamber should not cause a catastrophic failure; however, due to the slightly wider throat specifications in NATO chambers, firing either 7.62 or 5.56 NATO ammunition in .308 or .223 spec chambers will result in greater wear on the barrel throat and will reduce its service life.
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This is wrong. The max pressure for .308 Win is higher than that of 7.62 NATO. Suggest the mods delete this thread or at least unsticky it as it is pretty garbled and contains bad info.
 
VanIsler said:
This is wrong. The max pressure for .308 Win is higher than that of 7.62 NATO. Suggest the mods delete this thread or at least unsticky it as it is pretty garbled and contains bad info.
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Not quite. SAAMI does list these cartridges as being safe to interchange. There are some things to consider, but it has been pointed out that I misunderstood the issue, which isn't the same as the .223 vs. 5.56 issue.
 
Wikipedia has a good write up on this

5.56 mm NATO versus .223 RemingtonThe 5.56 mm NATO and .223 Remington cartridges and chamberings are similar but not identical. Military 5.56mmx45 cases are often made thicker and therefore have less case capacity.[17] However, the NATO specification allows a higher chamber pressure. NATO EPVAT test barrels made for 5.56 mm 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 20,000 psi (140 MPa) difference in pressure measurements. This means the NATO EPVAT maximum service pressure of 430 MPa (62,000 psi) for 5.56 mm NATO, is reduced by SAAMI to 55,000 psi (380 MPa) for .223 Remington.[18] 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 5.56 mm NATO.

The 5.56 mm NATO chambering, known as a NATO or mil-spec chamber, has a longer leade, 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 (Rock River Arms)[19] or the ArmaLite chamber, which are designed to handle both 5.56 mm NATO and .223 Remington equally well. The dimensions and leade of the .223 Remington minimum C.I.P. chamber also differ from the 5.56 mm NATO chamber specification.

Using commercial .223 Remington cartridges in a 5.56 mm NATO chambered rifle should work reliably, but generally will not be as accurate as when fired from a .223 Remington chambered gun due to the longer leade.[20] Using 5.56 mm 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 SAAMI recommends against the practice.[21][22] Some commercial rifles marked as ".223 Remington" are in fact suited for 5.56 mm NATO, such as many commercial AR-15 variants and the Ruger Mini-14 (marked ".223 cal"), 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 5.56 mm NATO ammunition.[23]

It should also be noted that the upper receiver (to which the barrel with its chamber are attached) and the lower receiver are entirely separate parts in AR-15 style rifles. If the lower receiver has either .223 or 5.56 stamped on it, it does not guarantee the upper assembly is rated for the same caliber, because the upper and the lower receiver in the same rifle can, and frequently do, come from different manufacturers – particularly with rifles sold to civilians or second-hand rifles.

In more practical terms, as of 2010 most AR-15 parts suppliers engineer their complete upper assemblies (not to be confused with stripped uppers where the barrel is not included) to support both calibers in order to protect their customers from injuries and to protect their businesses from resultant litigation.
 
petew said:
After reading 11 pages I know less than when I started.
Pete
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Here is what you need to know:
- 5.56 runs at higher pressures than .223 - evidence, if required, is the different gas port sizes in AR-15s for each calibre. Ports sized for .556 will work poorly with commercial .223 ammo but will run fine with 5.56.
- Most / many ".223" chambers are cut generously in case someone runs the wrong (5.56) ammo in it. This is why people get away with running 5.56 in .223 chambers.
- In a properly-cut SAAMI-spec .223 chamber, 5.56 will run at proof-load pressures (>76Kpsi). This is a) at least a little dangerous and b) shortens the lifespan of your gun.
 
Thanks. As I understand it now I am safer/ less risk, sticking to 223 ammo in my Rem 700, and I can reload 5.56 brass to use in the 700 /223, providing I am working up a safe load, of course, due to the internal volume being diferent.
Pete
 
petew said:
As I understand it now I am safer/ less risk, sticking to 223 ammo in my Rem 700
[...]
and I can reload 5.56 brass to use in the 700 /223, providing I am working up a safe load, of course, due to the internal volume being diferent.
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1) yes
2) yes, although you may find that military brass will have similar volumes to commercial - it just depends on the respective brands. So, as always, you work up the load that works with your brass in your chamber. Always best to use one brand for a given load ( and one lot - Lapua, for example, changed their case volume upwards a few years ago ), but only critical if you are near max.
 
Self preservation check:

Been shooting 5.56mm Nato in 223 chambered rifles Ar15, Tikka T3, mini 14, Rem 700, Savage 11f for 25 years.

Tens of thousands of rounds fired.

Still never wore out a chamber or bore.

Still have fingers.

Still have teeth.

Still have eyeballs.

Still will take that big death defying risk next range day.

Moe
 
Moe said:
Self preservation check:

Been shooting 5.56mm Nato in 223 chambered rifles Ar15, Tikka T3, mini 14, Rem 700, Savage 11f for 25 years.

Tens of thousands of rounds fired.

Still never wore out a chamber or bore.

Still have fingers.

Still have teeth.

Still have eyeballs.

Still will take that big death defying risk next range day.

Moe
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Ditto.

Except for that 25 number... :D
 
MasterMC said:
It's not dimensions of the cartridges, the chamber and throat dimensions of 5.56 NATO and .223 REM are different. I've ever seen signs of over pressure when shooting 5.56 NATO rounds in my .223 REM match chamber rifle, never again.
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Bullet and cartridge diameter still the same as per SAAMI the inside of the brass on 5.56 NATO is thicker for full auto firearms used in the military/law enforcement to strengthen the cases. Over pressure can be caused by higher loads in 5.56 brass. Mental Note: if using 5.56 brass vs 223 Rem brass lighten load problem solved. and once again any reloading manual will tell you that. :)
 
gunnie1983 said:
Bullet and cartridge diameter still the same as per SAAMI the inside of the brass on 5.56 NATO is thicker for full auto firearms used in the military/law enforcement to strengthen the cases. Over pressure can be caused by higher loads in 5.56 brass. Mental Note: if using 5.56 brass vs 223 Rem brass lighten load problem solved. and once again any reloading manual will tell you that. :)
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The brass is thicker and pressure runs about 3k higher but the real danger comes from the longer headspace required for 5.56. If a long bullet 5.56 round is put into a shorter .223 chamber the bullet can be rammed into the rifling (throat) which can cause an overpressure when the rifle is fired, which is the cause of primers blowing out, etc.
 
I have a ar15 with a north eastern arms 14.5'' barrel for 5.56 nato and i have shot both with no problems . i know if u have a .223 rem and fire 5.56 nato it might work but you might have the casing expand in the chamber and gets stuck but you can also shoot 5.56 out of a rifle chambered for .223 wylde
 
its not very scientific but could someone who owns both 223 in a bolt action rifle and a 556 chamber in a semi auto military styled rifle please shoot both types of ammo in each rifle over a chronograph the same day under the same conditions and let us know please?most of the time but not always will higher chamber pressures translate into higher velocity.not definitive but perhaps a bit revealing.
 
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