For those that don't know 5.56 is a much better ammo than .223
 

If you have a rifle that can shoot both .223 and 5.56 than you should opt for the 5.56. This information is for those who are new to Assualt Rifles that can shoot both ammo and don't realize they can use 5.56 (in my experience I have seen a lot of AR guys shoot specifically only .223). Keep in mind 5.56 and .223 are not identical and you should consult your manual before you try to shoot 5.56.

The reason 5.56 is better is because they typically have higher velocity and chamber pressure than .223. 5.56 has a maximum service pressure of 62,366psi while .223 ha 55,000psi.

5.56 is a approved US Military/NATO ammunition, so I'm sure that tells us its good enough for war while .223 is not.

The good part is 5.56 is priced pretty much the same as .223. Once you shoot it you will notice and hear the difference between the ammo.

Also for those who have ARs (ie. Rock River Arms, Armalite) that can shoot both .223 and 5.56 and use .223 you are losing some accuracy by using .223. This has been proven.

A lot depends on what your goals and objectives are. Some of what you are saying here isn't entirely accurate, or perhaps applicable, especially since most shooters aren't setting out to the range to fire on live targets.

Almost all match grade and high grain ammo for ARs is .223. At longer ranges, this ammo generally is far more consistent than, for example, M193.
I would like to see some proof that accuracy is lost with match grade .223 when compared with military issue 5.56.

With that said, 5.56 is more fun to shoot. About 75% of what comes out of my rifles is that caliber. The extra punch does have that added cool factor. If I were stuck in a SHTF situation, I would grab a box of M193 before anything else, but since we haven't reached a state of true anarchy yet, I don't know if I would advocate the need for 5.56 to put bigger holes in paper down range.
Shoot with what you are comfortable with.

For all new AR owners, make sure your rifle is chambered for 5.56 . Rifles chambered in .223 are not designed to handle the increased pressure of 5.56 NATO.

Here is some information from Winchester.

Paul Nowak5/4/2001.223 Rem VS 5.56mm

There are a lot of questions about these two cartridges. Many people think they are identical - merely different designations for commercial and military. The truth is that, although somewhat similar, they are not the same and you should know the differences before buying either cartridge.

• The cartridge casings for both calibers have basically the same length and exterior dimensions.
• The 5.56 round, loaded to Military Specification, typically has higher velocity and chamber pressure than the .223 Rem.
• The 5.56 cartridge case may have thicker walls, and a thicker head, for extra strength. This better contains the higher chamber pressure. However, a thicker case reduces powder capacity, which is of concern to the reloader.
• The 5.56mm and .223 Rem chambers are nearly identical. The difference is in the "Leade". Leade is defined as the portion of the barrel directly in front of the chamber where the rifling has been conically removed to allow room for the seated bullet. It is also more commonly known as the throat. Leade in a .223 Rem chamber is usually .085". In a 5.56mm chamber the leade is typically .162", or almost twice as much as in the 223 Rem chamber.
• You can fire .223 Rem cartridges in 5.56mm chambers with this longer leade, but you will generally have a slight loss in accuracy and velocity over firing the .223 round in the chamber with the shorter leade it was designed for.
• Problems may occur when firing the higher-pressure 5.56mm cartridge in a .223 chamber with its much shorter leade. It is generally known that shortening the leade can dramatically increase chamber pressure. In some cases, this higher pressure could result in primer pocket gas leaks, blown cartridge case heads and gun functioning issues.
• The 5.56mm military cartridge fired in a .223 Rem chamber is considered by SAAMI (Small Arm and Ammunition Manufacturers Institute) to be an unsafe ammunition combination.

Before buying either of these two types of ammunition, always check your gun to find what caliber it is chambered for, then buy the appropriate ammunition. Most 5.56mm rounds made have full metal jacket bullets. Performance bullets - soft points, hollow points, Ballistic Silvertips, etc. - are loaded in .223 Rem cartridges. Firing a .223 Rem cartridge in a 5.56mm-chambered gun is safe and merely gives you slightly reduced velocity and accuracy. However we do not recommend, nor does SAAMI recommend, firing a 5.56mm cartridge in a gun chambered for the .223 Rem as the shorter leade can cause pressure-related problems.

Winchester Law Enforcement Ammunition
East Alton Illinois

This really doesn't address comparisons between military issue 5.56 and match grade .223. It is more of a commentary on the differences of the calibers.

Read the 5th Bullet.

I don't have a manual that came with my "Colt Sporter MATCH HBAR CAL .223" . It is a pre-ban weapon and on the topside of the barrel it says: O MP 5.56 NATO 1/7 HBAR. Does this mean the obvious ? Or does it only indicate the barrel is suitable for 5.56, but the chamber may not. Thanks in advance.

Someone correct me if I am wrong. I believe any assault rifle that was originally designed for military use (which means probably all AR15 style weapons) can shoot 5.56. My guess of course would be that you can shoot 5.56. When you do shoot 5.56 you will notice the difference between that and .223. I should have corrected my title, it should say if your rifle is chambered for 5.56 it will be better to use 5.56 versus .223. If you are still not comfortable putting 5.56 in your rifle give Colt a call.

Good to know EVS. Thanks. Now the only problem is finding bulk 5.56. .223 is available everywhere.

Surprisingly I found Winchester 5.56 at a Walmart for $10.95 for 20 rounds only! I bought about 30 boxes of it!

Try this website AmmoEngine: 7.5x55mm Swiss (Schmidt-Rubin), Instock For Sale Premium & Discount Ammunition, Ammo Deals

Good deal here... http://www.cabelas.com/cabelas/en/te...box.jsp.form23