.308=7.62x51? .223=5.62? Help?

[bergman]

Ok, I was looking for some knowledgeable advice.

I know for reloading, these are NOT the same, as in headspace, but are they interchangable for new cartridges?

Ditto for the 223 vs 5.62?

I want to know if I can plink surplus ammo through my otherwise hunting/varmint rigs without too many complaints from my rifles!

[Metalmike123]

As I understand it the 5.56 is the same case dimensions as .223 but thicker walls and much higher pressure, so I wouldn't.

[wally338]

I shoot surplus ammo lots no issues at all in both bolt and semi auto guns.

[Leeper]

There is absolutely nothing wrong with shooting either of the cartridges mentioned in their military configuration through any standard sporting rifle. Any differences in dimensions are so slight that they hardly bear mentioning. In the case of the 5.56/223, the difference in headspace is .0001" (one ten thousandth of an inch) so it is of no consequence. Leeper

[Metalmike123]

I'll retract my statement, 5.56 apparently do have thicker case walls but similar pressures

[nick0danger]

My understanding shoot, 556 in a 223 but don't shoot 223 in a 556.

[rwm1273]

From Wikipedia:

5.56 mm NATO versus .223 Remington

The 5.56 mm NATO and .223 Remington cartridges and chamberings are similar but not identical. Military 5.56×45mm cases are often made thicker and therefore have less case capacity. 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. 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) 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. 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. 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.

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.

Although not identical, the 7.62×51mm NATO and the commercial .308 Winchester cartridges are similar. And even though the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) considers it safe (by not listing it) to fire the NATO round in weapons chambered for the commercial round, there is significant discussion about compatible chamber and muzzle pressures between the two cartridges based on powder loads and wall thicknesses on the military vs. commercial rounds.

[catnthehat]

I n have fired Nato rounds from several different manufacurers accurately in my rifles right out to 1K, but I do not shoot semis.
I'm not sure if a difference would be noticed or not.
The big thing about hand loading the brass is to make sure of the specs used match the brass, that's it.
Cat

[elkhunter11]

My understanding shoot, 556 in a 223 but don't shoot 223 in a 556.

Given that the 223rem is the lower pressure load, you won't have any issues shooting 223rem in a 5.56 rifle.

[alpining]

Originally Posted by Metalmike123

I'll retract my statement, 5.56 apparently do have thicker case walls but similar pressures

Correct, but this does have consequences for handloading: Thicker case wall means lower volume, which means higher pressure IF you use the same powder charge. Military brass generally needs to use a smaller powder charge, all other things being equal.

[Leeper]

The .032" difference in the length of the lead on the 5.56 chamber may very well increase pressures but I have never seen any evidence that it is of any real consequence. I recently checked some 223 case volumes and found that Lake City 5.56 brass was actually lighter than Winchester commercial brass and held less water; this kind of shoots down the "heavier case walls" story. There is a tremendous amount of BS in the shooting world which is repeated often enough that it becomes gospel.
Wikipedia makes some useful information available to those who wish to access it but it also makes unsubstantiated opinions available.
By the way, the aforementioned Lake City rounds, when fired in my 223, actually seemed to be quite mild. Go figure. Leeper

[hunterbobthebuilder]

So does this mean my 300 win will work in my 22?

[sikwhiskey]

Originally Posted by hunterbobthebuilder

So does this mean my 300 win will work in my 22?

Of course it will, you just need to use a bigger hammer for loading it.
5.56 and 223 not enough difference to worry about.

[alpining]

Originally Posted by Leeper

The .032" difference in the length of the lead on the 5.56 chamber may very well increase pressures but I have never seen any evidence that it is of any real consequence. I recently checked some 223 case volumes and found that Lake City 5.56 brass was actually lighter than Winchester commercial brass and held less water; this kind of shoots down the "heavier case walls" story. There is a tremendous amount of BS in the shooting world which is repeated often enough that it becomes gospel.
Wikipedia makes some useful information available to those who wish to access it but it also makes unsubstantiated opinions available.
By the way, the aforementioned Lake City rounds, when fired in my 223, actually seemed to be quite mild. Go figure. Leeper

Agreed that there is a bit much of the second hand info floating around. But, I have read about the difference in case volume with military brass in reloading manuals, and that is something I never discount.

To be clear, your observation that the LC brass "holds less water" means smaller volume for those cases, which DOES support the "use smaller charge for military brass" idea. Whether it is thicker walls or not (overall mass might not be the best measure of wall thickness anyways), case volume is what matters. Mass is a poor proxy measure for case volume, as has been shown by Jerry at Mystic Precision, I believe.

[Okotokian]

Thanks for this. I always wondered.

[Leeper]

Sorry, I mis-typed. The Lake City brass was lighter and held MORE water than did the Winchester brass. The Lake City capacity was exactly the same as Remington brass. So, the case volume was not less with the military brass I had on hand. Other makes of 5.56 mm might very well be smaller in capacity. It is worthwhile to note that the difference in volume was on the order of 2%. That amount of difference was present among different makes of commercial brass as well.
By the way, even loading manuals will pass along unsubstantiated and erroneous information. Leeper

[alpining]

Who can you trust, eh Leeper?!

All the more reason to do your pressure testing with exactly the type of brass that you intend to reload, I guess.