.223 vs. 5.56

[Troublco]

Also, and you can all correct me if I am wrong, the 5.56 has a longer throat in the chamber

If I remember correctly, external dimensions of the cases is exactly the same, but 5.56 casings are slightly thicker, mostly through the shoulder, causing them to have less internal volume, therefore developing more chamber pressures with the same ammount of powder. if your barrel says 5.56, your good to go for both rounds, if it says .223, only shoot .223!

I'm no expert, but my understanding is that the pressure is the big issue. The Mil brass has a thicker case web and walls which does raise the pressure from an identical load in .223. Externally the dimensions are identical; but the mil brass will take more abuse (at least the first time). The other thing I've heard over the years, although I've never taken the time to confirm it personally, is the chamber for a 5.56 gun will be looser than a .223 owing to the desire of the military for the gun to continue to work when dirty, and that it will have a longer throat. They want the gun to continue to work in battlefield conditions, so the chamber is opened up a bit. The Brits were famous for this on a lot of the Lee-Enfields; I have one of those where the fired brass swells out almost as far as the case rim. Manufacturers of civilian .223's aren't concerned about the same things, so the chambers are SAAMI spec.

I've also found most Mil 5.56 brass to be harder than a lot of Civ brass, with the exception of the Federal-produced LC brass used for the newer frangible training ammo. That is fairly soft and reforms/reloads rather well.

The one caveat to all this is the Wylde chamber. This is sort of a compromise between the two; as I understand it it's basically a .223 chamber with a longer throat and will shoot either .223 or 5.56 ammo fine.

[hip55]

[MarkCO]

I sure like pictures, saves a lot of words.

Get your AR in .223 Wylde and call it good for both with better everything.

[Hoosier]

One of mine is a Rock River varmit setup, I'm guessing it's Wylde but I need to find out for sure.

The other one, I really don't know... an former army armorer set it up.

H.

[sniper7]

One of mine is a Rock River varmit setup, I'm guessing it's Wylde but I need to find out for sure.

The other one, I really don't know... an former army armorer set it up.

H.

I think RRA....well at least for the 4 or 5 years has always used wylde chambers.

[cowboykjohnson]

My RRA upper is about 5 years old and has the Wylde chamber.

[cowboykjohnson]

[quote=sniper7;167940]okay quickly since I gotta get going...Rodizio grill here I come!!!!
quote]
How was Rodizio's? I love that place!

[Hannu]

I would consider difference between .223 and 5.56 like this :
-If you want to kick dust or empty beer cans with steel case or milspec ammo, you want to get 5.56 chamber.

-If you load all your own ammo and feed it from magazine (or shoot quality factory stuff), you care what kind of groups your rifle shoots and you shoot a lot so you care about barrel life - go with .223 Rem.
With .223 Rem, you can load all match heavy bullets (like 69gr MK or CC) as long as your mag allows and still not get rifling contact, so why use any longer freebore in general use ?

.223 Wylde was developed for hi-power. You can load 90gr MatchKing really long before having rifling contact, have more room for powder but you can not feed them from magazine. It is a brilliant chambering, for use it is developed.
It is better for general civilian use than 5.56, but accuracy (specially with light bullets) and barrel life are much more limited compared to .223 Rem.
.223 Wyldes long freebore is never a good thing for accuracy (except mentioned use above) or barrel life, but just the opposite. Wylde has .224" diameter freebore like .223 Rem, which makes it (in my opinion) unsuitable for military rifles.

Reason why many manufacturers like to use .223 Wylde in general purpose rifles: you usually get better accuracy with Wylde than 5.56, but Wylde is still pretty forgiving if you use little too fast powder, or if you want to shoot milspec ammo. Consumer protection and responsibility is at pretty high level in US.
In Europe, firearms will be CIP proofed - responsibility is transferred mainly to proof house. Almost all European AR-15 rifles are chambered (real chambering) for .223 Rem CIP, which is pretty much the same as .223 Rem SAAMI, except maximum pressure.

Other semi-auto military rifles than AR-15 can use much tighter chamberings, which are pretty close to SAAMI .223 Rem, but they are of different design.

You should also note, in Europe .223 Rem max pressure is 62.000 PSI = the same as for 5.56 Nato in US.
We have shot many M193 milspec ammo types in .223 Rem CIP minimum spec. pressure gun, but never got average over 62.000 PSI. With M855 ammo, there are however several that generate around 67.000 PSI.
.223 proof pressure is 81.000 PSI, so you are not gonna blow your rifle with few 5.56 Nato rounds. Of course, shooting overpressure rounds will wear your rifle faster. The same works other way too - if you keep pressure level (with handloaded ammo) at around 45.000 PSI or less, you can usually greatly increase your bolt & barrel lifespan.
I have not heard, that any S&W, Bushmaster, Colt, DPMS, Stag Arms or STI rifles would have exploded in proof firing.
In Europe, they must fire 2x 81.000 PSI proof shots with each and every rifle before they can sell them.
Again however, if your rifle is poor quality, for example not all bolt lugs contacting barrel extension, you can blow your rifle with pretty low pressure ammo.

Just my 2 cents