.223 REMINGTON VS. 5.56 NATO: WHAT YOU DON’T KNOW COULD HURT YOU

[Bruce Jackson]

http://www.humanevents.com/2011/02/15/223-remington-vs-556-nato-what-you-dont-know-could-hurt-you/

http://tinyurl.com/cl53vvm

.223 REMINGTON VS. 5.56 NATO: WHAT YOU DON’T KNOW COULD HURT YOU

By: Human Events
2/15/2011 03:01 AM

Is firing a 5.56 NATO cartridge in your .223 Remington chambered AR15
dangerous? Or do Internet forum-ninjas and ammunition companies
selling you commercial ammo instead of surplus overstate the dangers?
Believe it or not, a real danger exists, and some gun owners who think
they are doing the right thing may not be safe.

The Cartridges

The .223 Remington and 5.56×45 NATO cartridges are very similar, and
externally appear the same. But there are some differences that lie
beneath the surface.

The 5.56 case has thicker walls to handle higher pressures, meaning
the interior volume of the case is smaller than that of a .223. This
will alter the loading data used when reloading 5.56 brass to .223
specs.

Some 5.56 loads have a slightly longer overall length than commercial
.223 loads.

The Chambers

The significant difference between the .223 Rem and 5.56 NATO lies in
the rifles, rather than the cartridges themselves. Both the .223 and
5.56 rounds will chamber in rifles designed for either cartridge, but
the critical component, leade, will be different in each rifle.

The leade is the area of the barrel in front of the chamber prior to
where the rifling begins. This is where the loaded bullet is located
when a cartridge is chambered. The leade is frequently called the
“throat.”

On a .223 Remington spec rifle, the leade will be 0.085”. This is the
standard described by the Sporting Arms and Ammunition Manufacturers’
Institute, Inc. (SAAMI). The leade in a 5.56 NATO spec rifle is
0.162”, or almost double the leade of the .223 rifle.

A shorter leade in a SAAMI spec rifle creates a situation where the
bullet in a 5.56 NATO round, when chambered, can contact the rifling
prior to being fired. By having contact with the rifling prematurely
(at the moment of firing), chamber pressure can be dramatically
increased, creating the danger of a ruptured case or other
cartridge/gun failure.

The reverse situation, a .223 Rem round in a 5.56 NATO gun, isn’t
dangerous. The leade is longer, so a slight loss in velocity and
accuracy may be experienced, but there is not a danger of increased
pressures and subsequent catastrophic failure.

How serious is the danger of firing 5.56 ammo in .223 guns? Dangerous
enough that the SAAMI lists 5.56 military ammo as being not for use in
.223 firearms in the technical data sheet titled “Unsafe
Firearm-Ammunition Combinations.”

ATK, the parent company of ammunition manufacturers Federal Cartridge
Company and Speer, published a bulletin entitled “The Difference
Between 223 Rem and 5.56 Military Cartridges.” In this bulletin, ATK
stated using 5.56 ammo in a .223 rifle could result in “…primer pocket
gas leaks, blown cartridge case heads, and gun functioning issues.”

However, the danger may be lower than SAAMI or ATK suggest. In
Technical Note #74 from ArmaLite, the company states “millions of
rounds of NATO ammunition have been fired safely in Eagle Arms and
ArmaLite’s® SAAMI chambers over the past 22 years,” and they have not
had any catastrophic failures.

According to ArmaLite:

“Occasionally a non-standard round (of generally imported) ammunition
will fit too tightly in the leade, and resistance to early bullet
movement can cause elevated chamber pressures. These pressures are
revealed by overly flattened primers or by powder stains around the
primer that reveal leaking gasses.”

What Do You Have?

So, if you own a rifle chambered for the .223 for 5.56, do you know
for which caliber it is really chambered?

Many match rifles are chambered in .223 Remington (SAAMI specs) for
tighter tolerances, and theoretically better accuracy.

Many of the AR-15’s currently sold on the market are made for the 5.56
NATO cartridge. If you own one of these, you should be fine with any
.223 or 5.56 ammunition.

However, ATK dropped this bomb in the bulletin on the .223/5.56:

“It is our understanding that commercially available AR15’s and M16’s
– although some are stamped 5.56 Rem on the receiver – are
manufactured with .223 chambers.”

So, even if your AR is stamped 5.56, is it really? Check your owner’s
manual or call the company directly and make sure you get an answer
you feel comfortable with.

As if the confusion regarding the .223 vs 5.56 chambers wasn’t enough,
there is a third possibility in the mix, that is being used by at
least one major manufacturer. The .223 Wylde chamber is a modified
SAAMI-spec .223 chamber that allows for the safe use of 5.56 NATO
rounds, but maintains tighter tolerances for better accuracy.

Yeah, yeah… What’s the bottom line?

Here’s the bottom line. If you want to follow the safest possible
course, always shoot .223 Remington ammunition. The .223 Rem
cartridge will safely shoot in any rifle chambered for the .223 or
5.56.

If you want to shoot 5.56 NATO rounds, make sure you have a rifle
designed for the 5.56 military cartridge. Shooting 5.56 in a normal
.223 Rem rifle can result in bad things.
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