A 556 NATO cartridge (left) and 223 Rem cartridge (proper). Richard Mann

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With regards to the 223 vs 556, it’s not a lot about which one is finest, however concerning the variations between them. The 223 Remington and 5.56 NATO cartridges have similar case dimensions however will not be fully interchangeable. They’re considerably like similar twins who’re visually indistinguishable however as completely different as some other two human beings. Sorting all of it out is difficult as a result of case dimensions will not be the one factor that determines interchangeability. The query of 223 vs 556 all comes all the way down to load strain and the way a rifle’s chamber is minimize into every barrel. So, let’s see if we will untangle a few of this confusion.

The 223 Remington

A box of 223 Rem ammo on a white background with two cartridges next to it.
The 223 Remington is likely one of the hottest varmint and smaller-size big-game cartridges round. Richard Mann

Growth of the 223 Rem started within the late Fifties with a purpose of making a small-caliber rifle cartridge for the U.S. army. After a interval of testing in 1961, through which twice as many shooters certified professional with the ArmaLite AR-15 in 223 Remington than did shooters with the M-14, the 223 was advisable for adoption. In 1962 Remington submitted the cartridge to SAAMI (Sporting Arms and Ammunition Institute) for approval, and a yr later the corporate launched their first 223 Remington rifle. Curiously, that rifle was the pump-action Remington Mannequin 760. Since then, the cartridge has turn into some of the common for varmint and smallish big-game searching, in addition to for private safety and leisure and competitors capturing. Nonetheless, the army gave the brand new cartridge a special title—Cartridge, 5.56mm ball, M193—which is now the 223 vs 556 confusion started.

The 5.56x45mm NATO

A box of Hornady 556 ammo on white background with two loose cartridges nearby
The 5.56 NATO cartridge is an offshoot of the 223 Rem, not the opposite means round. Richard Mann

Some imagine the 5.56 NATO was the unique army cartridge and that the 223 Remington was the civilian offshoot. That’s not the case. In 1970, NATO affiliated nations agreed on a smaller-caliber cartridge to exchange the 7.62x51mm NATO, which has similarities to the 308 Winchester, and that’s one other however related story. The idea for the brand new cartridge was the 223 Remington, and it was optimized for a light-weight machine gun created by FN. The 5.56x45mm was standardized by NATO in 1979, and after that, the U.S. Navy reconfigured their M16s for five.56 NATO compatibility. Right this moment, AR-15s—the semi-automatic model of the M16—will be chambered for 223 Remington, the 5.56 NATO, or the 223 Wylde. We’ll get to the 223 Wylde shortly.

223 vs 556: What’s the Distinction?

The cartridge circumstances of the 223 Rem and 5.56 NATO seem similar on the surface, however 556 circumstances can have minutely thicker case partitions. One other distinction is in strain. SAAMI has a longtime most common strain ranking of 55,000 psi for the 223 Remington and 57,500 psi or much less for all AR-15 suitable cartridges. There are not any SAAMI 5.56 NATO strain specs, however the cartridge typically operates at round 62,000 psi, relying on the load. Clearly, the AR-15 can clearly deal with 62,000 psi as a result of there are many AR-15s chambered for the 5.56 NATO. So, why does it matter.

It issues as a result of the chamber that’s minimize contained in the barrel of a 223 vs 556 are completely different. So far as the portion of the chamber that encases the cartridge case, they’re the identical; it’s the chamber minimize previous the case mouth that’s completely different. A chamber in a 5.56 NATO barrel has an extended throat, which is the phase of the chamber between the case mouth and the place the rifling lands taper from nothing to the bore diameter of 0.219-inch/5.56 millimeters. This further house permits the barrel to resist the upper pressures of the 5.56 NATO. It’s that easy. What’s not as easy is the interchangeability.

Are 223 and 556 Interchangeable?

Two 556 cartridges on the left, standing next to two 223 cartridges on the right.
The 556 (left) and 223 (proper) look similar; however they aren’t completely interchangeable. Richard Mann

It’s completely protected to shoot 223 Remington ammunition in a 5.56 NATO rifle, however in some circumstances, precision will be lower than stellar. However, it’s thought of unsafe to shoot 5.56 NATO ammunition in a 223 Remington rifle. You see, the 5.56 NATO cartridge will produce about 62,000 psi in a 5.56 NATO chamber, and that’s OK. However within the 223 Remington chamber with the tighter throat, pressures can exceed 70,000. That’s not OK. You may get by doing it one time, and even 10 occasions, however you additionally may blow your gun aside and severely jeopardize physique elements like eyes and fingers in case you do it simply as soon as.

The potential for poor precision when capturing 223 Remington ammunition in a 5.56 NATO rifle and the fear of an explosive disassembly when capturing 5.56 NATO ammunition in a 223 Remington rifle is what led to the 223 Wylde. The 223 Wylde isn’t a rifle cartridge and neither is it a kind of ammunition. The 223 Wylde is a specification for the reamer that cuts a chamber to supply a dimensional hybrid between the 223 Remington and the 5.56 NATO specs. It has turn into highly regarded in AR-15s as a result of it permits shooters to not fear in the event that they’re capturing 223 Remington or 5.56 NATO ammunition. It’s completely protected and customarily delivers good precision with each.

223 vs 556 for Handloaders

Now, simply whenever you assume you’ve bought this all this discovered, there’s extra to the story. For those who load your personal ammo, 5.56 NATO information is difficult to seek out, and whenever you do discover it, it’s probably similar to 223 Remington information from the identical supply. That is principally attributable to the truth that numerous of us use 5.56 NATO brass to load 223 Remington ammunition. And whereas its typically thought that 5.56 NATO brass has a lesser capability, that’s not at all times the case. This is the reason you start any loading mission with what’s referred to as “beginning masses” and work up.

I’ve seen circumstances headstamped for five.56 NATO and 223 Remington in the identical field of manufacturing unit 5.56 NATO ammunition. This will make cartridge identification problematic. Thankfully, whether it is certainly 223 Remington ammo and from a good manufacture, the case head might be marked 223 REM as a result of that’s what SAAMI mandates. If it’s marked in any other case, and it’s not 223 Remington ammo that you simply reloaded, don’t think about it protected to shoot in your 223 Remington rifle.

223 vs 556: Which is Finest?

For a very long time, the one 5.56 NATO ammunition accessible was army ammunition. That’s not the case. With so many AR-15s chambered in 5.56 NATO, there’s a small number of 5.56 NATO ammo loaded with extra standard sporting bullets appropriate for searching. However right here’s the factor: If the identical bullet sorts and weights are in contrast, the 2 cartridges carry out nearly as similar as they appear. That stated, there’s a considerably bigger number of 223 Remington masses to select from, and for this reason the 223 Wylde chamber minimize has turn into so common. In case your gun can safely shoot each, then your number of ammo decisions solely grows.

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