Thread: 223 or 5.56

Originally Posted by stretch

A simple google search of ".223 vs 5.56" leads to lots of sites saying they're NOT the same, and to mix them up is inviting trouble.

.223 Remington vs. 5.56 NATO: What You Don't Know Could Hurt You - Bearing Arms - Remington

because we all know the internet is never wrong......

When I see rifles by legitimate manufacturers stamp their rifles as both calibres are you telling me that they dont know what they are doing? Most of teh internet info comes form the USA and from what I have seen most wouldnt know a mm from a km so metric is a foriegn language to them.

An example would be European countries that actively discourage imperial measurements like France.

I am still open to the possibility that I am wrong, but if I could figure out how to post the photo.

I have here two brand new factory original rifles with the calibre stamp the says 308 (7.62x51) and another that says .223 (5.56x45) and a box of ammo from another manufacturer that has the same on it as well as a box that says 30/06, (7.62x63) These are not after market. They are manufacturer factory ammo in original new factory boxes and I use it to hunt with.

http://www.barnaul.co.nz/uploads/ima...2%20x%2051.jpg

http://www.barnaul.co.nz/uploads/ima...2%20x%2063.jpg

http://www.barnaul.co.nz/uploads/ima...%20reduced.jpg

It would be like saying a Weatherby Vanguard is better than a Howa 1500. Different names but that is about it. A few subtle cosmetic changes but thats about it.

I also found a web page extolling the virtues of buying a Ford Laser as it was better than a Mazda 323 as it was a better made "american car" than the Japanese one. They were actually made in the same factory and the only difference was badge work and price.

If you had read the link you would realise that it is fine to fire 223 in 5.56 so perfectly acceptable to sell and market 223ammo as suitable for both and mark a 5.56 chamber as 5.56 and 223 but not the other way around this is the point.

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Originally Posted by timattalon

because we all know the internet is never wrong......

We ARE on the internet, so if that's your approach, why would you take anyones advice for/against .223/5.56x45 compatibility on this forum over the many articles google can find?

Wikipedia isn't a perfect source either, but is a good starting point, as it is meant to have footnotes, citing the original sources of the information. Keep reading until you are satisfied you have found your answer. Or don't - just have a go and let us know how you get on.

https://en.wikipedia.org/wiki/.223_R...C3.9745mm_NATO

Short answer is that it (safety) depends on the chamber of any particular rifle.

Originally Posted by stretch

We ARE on the internet, so if that's your approach, why would you take anyones advice for/against .223/5.56x45 compatibility on this forum over the many articles google can find?

Wikipedia isn't a perfect source either, but is a good starting point, as it is meant to have footnotes, citing the original sources of the information. Keep reading until you are satisfied you have found your answer. Or don't - just have a go and let us know how you get on.

https://en.wikipedia.org/wiki/.223_R...C3.9745mm_NATO

Short answer is that it (safety) depends on the chamber of any particular rifle.

That does somewhat make sense. I see where its coming from now. There still seems to be some debate as to what is safe and what is not but it makes more sense than some of the earlier explanations. It does clearly state that both are dimensionally the same and that one is effectively a "hotter" load designed for a longer space before engaging rifling.

Originally Posted by veitnamcam

If you had read the link you would realise that it is fine to fire 223 in 5.56 so perfectly acceptable to sell and market 223ammo as suitable for both and mark a 5.56 chamber as 5.56 and 223 but not the other way around this is the point.

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That would work if it was marked 5.56 (223) but it chambered in .223 and also takes the 5.56x45. If I am reading that properly that is the other way around.

Originally Posted by timattalon

That would work if it was marked 5.56 (223) but it chambered in .223 and also takes the 5.56x45. If I am reading that properly that is the other way around.

How do you know which it is chambered in?
From a manufactures point of veiw it would be safest to ream everything to 5.56 lead no matter what is stamped on the barrel.

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Originally Posted by veitnamcam

How do you know which it is chambered in?
From a manufactures point of veiw it would be safest to ream everything to 5.56 lead no matter what is stamped on the barrel.

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That would make sense, It could be a similar situation to shotguns where you can use a 3" magnum in a shotgun chambered for 3.5" but you cannot do the other way around. But I would have thought they would have labelled the barrel 5.56 (223 if that was the case. But as long as I know I can use both it becomes moot what they have done. In this situation I know the manufacturer also makes larger calibres and apart from the chamber and diameter of the bore there is no other external changes to the rifles action etc so the action and barrel are capable of handling much larger calibres and pressures so perhaps for them it is a non issue.

5.56x45 is just a dimension, and could be used to describe any variation of 223 REM or 5.56mm NATO ammo/chambers. E.g. a barrel marked 223 REM/5.56x45 will most likely just be 223 REM.

Originally Posted by timattalon

I was under the impression that 556x45 was 223. Just like 7.62x51 is also 308 and 7.62x63 is 30/06.

8><-------

I will concede that usually those that make it labelled 556 are for military rate twists and have a heavier projectile (and sometimes a hotter load to push the heavier projectile, but My 223 will shoot and of them happily. It is more accurate with the lighter pills but that is due to the twist rate not the calibre.

This is well gone over, messy and filled with lots of dubious information.

Some thing to bear in mind is "philosophy of use" both then and now.

"then"

What I will say is the 556NATO is a highly loaded cartridge from the factory as it was driven there by the demands of the US army pushing the envelope as they wanted to reject the M16/ar15 in favour of keeping the M14. So the factor of safety is far less with the 556, unlike the 7.62x51/308w and 30-06 which in factory loads is pretty moderately loaded, hence it isnt really a fair comparison and a bit of a concern when I see such comparisons.

"now"

However, since its inception 50 years ado the AR15 556nato is probably one of the most tweaked and developed guns/cartridges ever? I suspect so. So today it maybe that the difference is moot. My suggestion is however until you can test that to make sure obey the "dont fire a 556nato in a 223 chamber rule" ie I have found 556 factory ammo with the odd round that have shown extreme stress inside a batch of otherwise normal looking 50 packs, once they have been fired in a 556nato chambered AR.

Playing safe is good I think.

Far out guys, i thought this was a simple question, maybe not.

The SAAMI standard 223 chamber drawing shows the following dimensions, in inches.
(these are just the dimensions relevant to this discussion, not ALL of them)
Freebore (or leade) length 0.025
Freebore diameter 0.224
Throat angle 3 degrees 10 minutes

There does not appear to be any SAAMI specification for the 5.56 NATO chamber, which is understandable. However, the specs for the JGS and PTG brands of 5.56 NATO chamber reamers are:
Freebore (or leade) length 0.0566
Freebore diameter 0.2265
Throat angle 1 degree 12 minutes

It has been well established by various experimenters that – with all other things being the same – a shorter freebore results in higher pressure.

It is also well established that – again, with all other things being the same – a freebore diameter of exact bullet diameter will result in higher pressures than a freebore diameter a couple of thou larger.

Somebody, somewhere, has probably done experiments to determine if variations in throat angle cause variations in pressure, but I am not aware of them.

However, it is easy to see that if a 5.56 .NATO cartridge is fired in a standard SAAMI spec chamber, the pressure is likely to be significantly higher than if it was fired in a NATO spec chamber. I am not going to even hazard a guess at how much higher, but I would suggest that if somebody is determined to shoot 5.56 NATO ammo in their 223 sporter, it would be prudent to get a chamber cast made first, to determine exactly what chamber dimensions it has.

Well from what I can read, there is also a second pressure pulse (apparently) So the first is the pulse that overcomes the bullet's inertia to leave the case, the second is when the bullet touches the lands, hopefully we all know about this? Many testers and equipment dont measure this second one which maybe the key one for the 556/223 issue as its so highly strung. So simply the books I have from knowledgeable ppl prepared to write about it in a book (ie are legally then liable as opposed to some knowall on a forum with a name like "jacksmackhead" who's "never had an issue") say you have to check and if need be ream the chamber to make it safe in all conditions. Add in that an AR15 gets extremely dirty, more abused and hence and hotter than a bolt action (who does 30~60 round mag dumps from a 223 boltie? in a minute?) so yeah sure. ie compare apples with apples.

My stance is to be safe and err on the side of caution, especially as there seems to be no real gain for most people.

"I am not going to even hazard a guess at how much higher" Some of the tests I have read suggest an AR15, dirty, on a hot day and abused (so hot) can exceed the bolt's test pressure done when new. Now this test pressure is done 1 or 2 times and never meant to be repeated and not 30 rounds (or more) from a mag dump.

On the other hand of course we dont see lots of pictures of f****ed AR's and ppl missing bits of hand / face.

There is a good kindle book series by Patrick Sweeney Gunsmithing the AR15 vol1 and vol2 and The Gun Digest book of the AR15, vol1 to 4, 6 books in all, worth reading IMHO.