It occurs commonly when a buyer chooses an AR-15 for sale chambered for .223 caliber and expects to shoot 5.56 ammunition in it. After all, many manufacturers actually print both calibers on the rifles, and it is in the manual that came with the rifle. So it is okay, right?

Unfortunately, the answer is no. The 5.56 will fit into the .223 chamber but, beyond this, the 5.56 in a .223 chamber is going to create problems. The cartridges may look the same, but the 5.56 Mil-Spec is hotter ammunition than .223. That is to say, the 5.56 has a higher chamber pressure. The chamber on the .223 is actually smaller, though not enough to prevent it from being inserted. It is small enough that it prevents the 5.56 case from expanding as it would in a 5.56 chamber.

What’s The Problem?

The firing of 5.56 ammo in a rifle chambered for .223 causes primer blow back to enter into the receiver decreasing reliability, as well as an increase in failures to eject spent cases. That is due to the hotter load of the 5.56. You may even have to use a rod down the barrel to remove the casing. Firing Mil-Spec ammunition may also crack the receiver posing a real hazard to the shooter and everyone nearby. It is far safer and provides greater reliability to purchase an AR-15 for sale chambered for 5.56 caliber ammo to begin with.

Different Chambers

Technically, you can fire 5.56 ammunition in a rifle chambered for .223, but why ruin the rifle and endanger yourself and others? If you want to use 5.56 Mil-Spec, buy a rifle chambered for 5.56. Basically, there are three types of chambers for AR-15 family of rifles.

• The first is the Mil-Spec 5.56 chamber used in the M16 and M4.
• Second is the .223 chamber commonly found in the AR-15 rifles.
• Third are the .223 Match chamber, commonly used in AR-15s by competition shooters.

The common .223 chamber are manufactured to Sporting Arms and Ammunition Manufacturers Institute Specifications (SAAMI). This chamber is ever-so-slightly smaller and tighter than Mil-Spec 5.56 chambers.

Match Chamber

The match chamber is the preferred chamber for professional competition shooters. Match chambers are not chrome lined.

The preferred weight of ammunition for match shooters and snipers is 77 grains and above. This ammo is slightly longer and lighter than AR ammunition. Using this grain of ammunition is not a problem in a rifle with a match chamber, but if you try to use it in the common .223 chamber problems occur due to the extra length. The extra length causes spillage of powder on the receiver and magazine when ejecting an unspent cartridge. To avoid the problems that may cost you a competition, purchase a match caliber .223 AR-15 for sale.

Mil-Spec Chamber

Mil-Spec 5.56mm chambers are always chrome lined in M16s and M4s for military use and typically are for the AR-15 equivalents. The 5.56mm Mil-Spec is slightly larger than common .223 SAAMI spec. This is due to the 5.56mm Mil-Spec being loaded hotter and having a higher chamber pressure.

Whereas it is highly discouraged to use 5.56 in a common .223 chamber, it is allowable to shoot the .223 ammunition as well as the 5.56 out of a rifle chambered for the 5.56 caliber, without any of the reliability or safety concerns of a .223 chamber. Just keep in mind, the .223 ammunition may not provide quite the accuracy at long distance as the 5.56 ammo. The .223 caliber ammo is slightly smaller and doesn’t fire as hot or with as much pressure. Plus the bore of the 5.56 is slightly larger. This advantage prevents the problems that may occur when ejecting a live cartridge, as can occur in a rifle chambered for .223.

Which Chamber Should I Buy?

If you are considering the purchase of an AR15 for sale, you may be wondering which chamber you should buy. If you are only going to be firing SAAMI ammunition, you can choose a common .223 AR-15 for sale. You should not fire 5.56 in a common .223 chamber.

If you participate in competition shooting, do not choose the common .223 SAAMI chambered AR-15. You will need the .223 Match Chamber AR-15 for sale in order to efficiently fire the required ammunition.

Finally, if you ever plan to shoot 5.56 mm Mil-Spec, you should purchase an AR-15 for sale that is chambered in 5.56. With the rifle chambered for 5.56 ammo, you will have the option of firing .223 ammo safely. The 5.56 chamber is the only chamber with this versatility. So if you have any thoughts of ever having to fire 5.56 ammunition, be safe and take the path that covers your bases. Purchase the AR-15 for sale chambered in 5.56.

GrabAGun is your source to buy guns online. Our extensive inventory includes a very large selection of the AR-15 for sale and AR15 accessories. Check out our blog post of must-have accessories for your AR-15. Whether you require an AR-15 for sale for competition shooting, hunting, or other uses; GrabAGun has the weapon you require.