AR Ammo: .223 or 5.56?

.223 cartridge tip

Since the “assault rifle” is such a popular platform in this day and age, I thought I would discuss ammo.

Ammo

The majority of civilian owned AR-15’s will shoot either the .223 caliber round invented by Winchester for the civilian market or the the 5.56 mm NATO round created for military use.

The .223 is considered a “varmint” round but does adequately in the area of self-defense. Some think the larger diameter .308 caliber is a better at stopping a man, while the .223 / 5.56 is easier to fire multiple rounds while staying on target.

I can personally attest to the last point. There is very little recoil on a .223 AR, and it stays on what you are aiming at. Little or no barrel rise.

Chambering

The chambering of the barrel is stamped somewhere on the barrel itself. It is actually better to pay attention to that rather than what is said on the lower / receiver (where the magazine is inserted).

Swapping

Now, here comes the tricky part. Part of the benefit of owning the AR platform can be the interchangeability of the 2 types of rounds. The problem is you have to do it a certain way, or there could be dangerous “boom” in the wrong place.

It is safe to fire both the 5.56 and the .223 rounds through a 5.56 barrel. It is not safe to fire a 5.56 round through a barrel stamped with .223. The reason has to do with the way the two cartridges are made and the length of the barrel chamber.

Reason

The 5.56 cartridge has a higher pressure. Therefore it is made with a thicker wall to handle that hotter load. The cartridge is also slightly longer.

Now we look at the chambering in the rifle barrel itself. Since the 5.56 is longer, the chambering in a 5.56 barrel is also longer. Conversely, the .233 chambering is obviously shorter.

The Wrong Way

When the longer 5.56 round is fired in the shorter .223 chamber, an unhealthy buildup of pressure can / will occur. This could cause the round to “rupture” in the chamber and could damage the gun and you

The Right Way

On the other hand, Shooting the shorter .233 round in the longer chambered 5.56 is not a problem. I’ve read that there may be a slight loss in accuracy if firing the .233 from a 5.56 barrel, but nothing major.

So there you have it. I’m sure there is more, but that’s all I know. Hope it helps.

Question

Do you shoot .223, 5.56, or both?

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