223 5.56 NATO Differences

[George9]

I have a XM15 BushMaster AR and stamped on the lower and the barrel is 223 5.56 Nato so I know it will take both.. What's the differences between the two? Does one shoot faster flatter bullet weight? energy? How may yards is it effective too? I know nothing about AR's! I'm a hand gun guy till now!George

 

[RKBAGUY]

Here... let me search on that for you.

The Differences Between .223 and 5.56 Rifle Cartridges and Chambering

 

[George9]

Thank You!! Sorry! G

 

[George9]

Gave it a read and what I'm getting out of it is that .223 Wylde will support the firing of both 223 Remington and 5.56mm NATO rounds without exceeding SAAMI specs.So does this mean that the cambering in my gun that takes both 223 and 5.56 NATO is really 223 Wylde ??? I'll have to hunt down power factors and some more info but thanks this is a good place to start.. G

 

[MichiganScott]

No, it does not. .223 Rem. can be fired in a NATO chamber but not the other way around.

The NATO chamber has the longer leade to accommodate higher pressures as required by the military to get the velocity desired.

 

[Doug M.]

If you do some searching on the web, you should be able to find "The Chart", done by Rob Sloyer (aka tactical yellow visor). Most of the tier one makers such as Colt, LMT, Bravo Company will have 5.56 chambering. Most other makers (Tier III) will have .223, and need a attention from a good chamber reamer to be appropriate for 5.56. The mere marking of a barrel as "5.56" does mean it is true. Ned Christiansen is a good source of info on such things. I saw one used at a Caputo class and metal came out of almost all of the barrels because they were not cut right for 5.56. He also makes the MOACKS (Mother of All Carrier Key Stakers) since only the better manufacturers stake that right.

Googling Ned and Dean Caputo will also lead you to good information. Going to ARFcom will likely result in the opposite. ARs come basically in two flavors: serious rifles for serious users (military, LE, hard shooters). These are the Tier I rifles. The others are Tier III. They can be used for that lighter level of use and may be perfectly satisfactory. Take them to a 3 day 1200+ round class and things get sideways in a hurry. I've seen this. It ain't funny. There are people out there who see >500,000 rounds down range yearly. That's some serious data.

 

[WR Moore]

Most other makers (Tier III) will have .223, and need a attention from a good chamber reamer to be appropriate for 5.56. .........

First and foremost, if the bore/chamber are chrome plated, it's going to take considerably more than a chamber reamer since the hard chrome is as hard as the reamer. Or at least the plating should be.

Secondly, not all chamber reamer makers use the exact same specs for a given caliber. I can't recall the exact specs, but 5.56mm reamers will cut a freebore of 0.025-0.030 inches longer than a .223 chamber. There are slight differences in the leade also in addition to the fact that not all chambers are cut identically regardless of tooling. So running a reamer into a chamber to see if it cuts proves little.

.223 and 5.56 use the same headspace gauges, so determination of what chamber it allegedly has will require a chamber cast and someone who knows what they're looking at. The use of Colt headspace gauges does not automatically indicate the chamber is a "real 5.56mm".

My personal .223/5.56mm rifle had paperwork from the factory that said I could use either. In 30 years, I've never cared or known what chamber it has and never had any issues regardless of what I fed it.

BTW, the root of the .223/5.56 thing is that the military chronographs their small arms ammo at 78 feet. They did that originally because of the technology of the day and haven't let progress change "the Army way" of doing things. Since .223 made the required velocity standard at 15 feet and didn't make it at 78 feet, they had to jack up the operating pressure of the round to make velocity.

 

[SMSgt]

Nearly every round fired in my Rem 788 .223 is from a reloaded 5.56 case. Once decrimped, resized in my RCBS .223 dies, and trimmed, they shoot fine. I don't load the heavier bullets found in some 5.56s, almost exclusively 55 grn spirepoints.

Your gun may be different. That's part of what reloading is about, finding what works best in your firearm.