5.56 NATO/. 223

[musketjon]

I'm not new to reloading. I have been shooting/ reloading for 30+ years, BUT I am thinking about getting an AR and loading for it. My questions thusly:
Can 5.56 and. 223 use the same die set? Is 5.56 and. 223 brass interchangeable or do they need to be segregated? It's my understanding that the main difference between the two is that 5.56 is higher pressure.
Jon

[dsltech]

Brass is the same

[liber]

Brass is the same

That's absolutely not true. The 5.56 is higher pressure, and as such typically has a thicker case wall thickness. The primers used are slightly different also.

It's important to know that when reloading as the volume inside the case is different and since the volume is different the same volume of powder will cause different pressures.

The dies are the same, and at least sold as such.

It is a good idea to separate .223 and 5.56 cases and load them accordingly, IMO, but the OP would be best to form their own opinion.

[musketjon]

Thank you for your expedient replies.
Jon

[Cowboy T]

The case dimensions are indeed identical. Thickness of the brass depends on whether it's GI or civilian brass. Lake City .30-06 military issue cases have slightly thicker walls, which results in slightly reduced case capacity. Same applies for Lake City 7.62 NATO vs. civilian .308 Winchester.

In .223 vs. 5.56, the main difference is pressure, and more specifically, where that pressure is measured. The other difference is the chambering of the firearm. From what I've been able to gather, 5.56 NATO chambers have a slightly longer freebore, or "leade", probably for the same reasons that Weatherby rifles tend to have it.

The result is that you can always safely shoot .223 Rem ammo in a 5.56 NATO chamber. Going the other way, though, is not guaranteed, though plenty of people routinely do it without incident.

So, if I were you, I'd just load to .223 specs and be done with it.

[dsltech]

from ar15.com reloading FAQ

Q: What is the difference in 5.56X45 NATO and .223 Remington brass? I can't find dies for 5.56 NATO cartridges.

A: The brass for both catridges is identical (except for the primer crimp in the military surplus brass), the chambers are slightly different. The throat of a 5.56X45 chamber is slightly longer than the SAAMI standard for .223 Remington. Refer to the Ammo Oracle for more details. Buy dies for .223 Remington.

http://www.ar15.com/forums/f_6/42_Reloading.html

223 is about 50-55k pressure while 5.56 is about 60+k pressure.

What Cowboy T said about certain brands have thicker case walls is true. Lake City brass will reload more times than most of the other brands. Most published reloading data is for 223. There are a couple of published load data for actual 5.56 but I have never tried it. Most just load as a 223.

[milotrain]

That's absolutely not true. The 5.56 is higher pressure, and as such typically has a thicker case wall thickness.

That is true with the bigger case and fairly rare in the case of .223 vs 5.56 nato. Look at the case capacities and weight of commercial vs NATO brass below. (article linked here)


First thing to realize is that initially there wasn't a governing body defining what a cartridge was, cartridges were designed by companies (.223 remington, .308 winchester) and rifles were built by those companies to run those specific cartridges. It's like how old records made by RCA could only be played on RCA players. Until a governing body was created to standardize cartridges, this governing body is SAAMI. So now cartridges are either SAAMI specified or called wildcats (which are cartridges designed by someone but not defined or governed by SAAMI). There is an exception which is that NATO has defined cartridges so that countries within the NATO alliance can share ammo and equipment, almost all NATO cartridges are simply SAAMI cartridges with further definitions or adjustments.

So .223 Remington is a SAAMI (commercial) specification and 5.56 NATO is a NATO (alliance) specification. Both use the same case dimensions but the NATO case allows for more variance. The other complication is that the .223 Remington was designed to shoot varmints from bolt rifles, so the SAAMI designation is generally directed at using light bullets 55gr and under, while the 5.56 NATO round is designed to kill bipeds and be used at night so it must handle heavier (read longer) bullets, bullets with petering armor tips (longer), and tracers (longer). Looking at this link you can see how varied bullets are for the .223 caliber. Additionally the NATO specification for 5.56 allows for more pressure in the case at firing than the SAAMI specification for .223. Pressure in a case is a function of the amount of powder in it, the case capacity and the resistance of the bullet to move down the bore. So if you took a big heavy bullet and stuffed it deep into a .223 case it will produce a lot more pressure than a small light bullet not taking up as much space. The primary concern with a .223 rifle shooting 5.56 ammo is that the heavy bullet gets set back when the bolt closes the round on a chamber with a shorter free bore, compressing the powder in the case above safe limits.

Lastly, and to really mess with your head, all of these specifications are interpreted by tool makers who then make a reamer to cut the chamber for a barrel. This means that a Clymer .223 reamer won't be the same as a JGS .223 reamer, and some .223 reamers might be able to make chambers that long 5.56 rounds will fire in (that's what the Wylde is). Looking at this link we see that the case dimensions for most of these reamers .223 and 5.56 included are quite similar. The difference is primarily in the "Free Bore" measurement between .223 reamers and 5.56 or .223 match reamers. Having a longer free bore is what allows you to shoot longer bullets set further out in the case. The NATO is built for this because of the longer penetrator and tracer rounds, but so is the .223 match chamber because of the 77gr and 80gr match bullets used for mid range shooting.

Therefore barrel makers will chamber their barrels in a number of different designations. In the AR platform if you get a .223 barrel it is likely that the free bore is shorter than a normal 5.56 NATO round would like, and certainly shorter than a tracer round would safely fire in (but you can't shoot tracers in California). But we know that the AR platform has enough barrel material that the pressure of a NATO round isn't a problem so we can assume that if the .223 AR barrel has enough free bore for whatever round we want to shoot (NATO or .223) then it should be safe. What we run into as a problem is .223 rifles which may not be safe with NATO lengths or NATO pressures. I don't know of many of them, and with the litigious nature of our society free bores on factory rifles are fairly long (so as not to create pressure problems that could be dangerous). But in any case if you prefer to make the choice to shoot something the barrel isn't marked to shoot you need to spend the time to measure the chamber and make an informed decision as to weather it is safe or not to proceed.

[liber]

That is true with the bigger case and fairly rare in the case of .223 vs 5.56 nato.

milotrain,

Are you saying that the volume is the same between .223 and 5.56 NATO ?

The volume chart you posted was for .223.

In the Hornady manual they list different loads for 223 and 5.56 NATO. I know some complain the Hornaday manual is off but unlike Speer they do list both 223 and 5.56 NATO.

Most all of the 5.56 NATO I've had is crimped, as in military ammo, much like 7.62x51 NATO.

I've considered the LC cases I have that have crimps on them to be 5.56 NATO.

I've read some of those links you posted but will go over that when I get home tonight.

[milotrain]

Reloading .223/5.56 for the AR platform in National Match conditions

My preference is to start with prepared brass from a known good supplier, PM me and I can give you some contacts. Or to start with good commercial brass (Winchester, Lapua, Nosler).

I don't like case gauges when sizing for the AR because a lot of .223 case gauges are much tighter than stock AR chambers. I prefer to buy a box of commercial ammo, fire it in the AR and then use those fired cases as a benchmark for my future sizing. I use an RCBS micrometer case gauge to check shoulder bump. I bump .002" when sizing and I use a Full Length sizer.

The Dillon sizing die is my favorite sizing die for the Wylde chamber as long as you size in an altered shell plate for a single stage or on a Dillon press (the Dillon shell plate is much thinner than a stock single stage shell plate. Do not start with the Dillon if you are sizing once fired unknown brass, you'll need to start with a small base die in that case (RCBS or Redding are my choices). This is why I prefer starting with well prepared or virgin brass.

[milotrain]

milotrain,

Are you saying that the volume is the same between .223 and 5.56 NATO ?

The volume chart you posted was for .223.

In the Hornady manual they list different loads for 223 and 5.56 NATO. I know some complain the Hornaday manual is off but unlike Speer they do list both 223 and 5.56 NATO.

Most all of the 5.56 NATO I've had is crimped, as in military ammo, much like 7.62x51 NATO.

I've considered the LC cases I have that have crimps on them to be 5.56 NATO.

I've read some of those links you posted but will go over that when I get home tonight.

Yes that's what I'm saying. The chart I posted has four different cases that are NATO cases (LC06, LC04, WCC99, FNM93-1) compared to commercial cases and their weights and volumes do not diverge significantly. Yes NATO brass has crimped primers, some commercial does as well. In the case of my LC 30-06 and my Winchester and Lapua 30-06: case walls, weights, and volumes are vastly different as you say.

[liber]

The chart I posted has four different cases that are NATO cases (LC06, LC04, WCC99, FNM93-1) compared to commercial cases and their weights and volumes do not diverge significantly.

There's a 2.5 grain spread between the cases on the chart. 2.5 grains is about 10 percent of a 223 load.

Also, the newer cases have a tendency to continue to get thinner and as such hold more volume.

I'm only saying that with a 2.5 grain spread, you can't just swap case and use the same load data, at least I wouldn't.

[milotrain]

I agree with you that you shouldn't swap cases and use the same load data when you are at the top end of the spectrum. No question. But the chart shows that a common misconception (that 5.56 NATO cases have thicker case walls and thus create higher pressures due to reduced powder column volume than .223 commercial) is not true. It is true for other military cases like the .30-06 though and this is likely where the misconception came from.

[micro911]

I use LC 5.56 brass to load for my AR. I have never had a problem with them. I do not load to maximum anyways. Only issue is the crimped primer pocket. I just have to swage the crimped primer pocket with the Dillon swager. It works very well.

[liber]

I agree with you that you shouldn't swap cases and use the same load data when you are at the top end of the spectrum. No question. But the chart shows that a common misconception (that 5.56 NATO cases have thicker case walls and thus create higher pressures due to reduced powder column volume than .223 commercial) is not true. It is true for other military cases like the .30-06 though and this is likely where the misconception came from.

I was reading that link, and agree the numbers show as you point out that the 5.56 NATO and 223 do not correlate to volume, but even the point out that there is a 2.5 gr spread and that the data can't be used.

I think the message there is do not use data across different cases whether they be 223 or 5.56 NATO.

It is interesting that some of the NATO cartridges have the highest volume, that I must admit. But I will say that the LC military brass I have definitely has fairly thin wall, and it gets dinged and bashed up more than my 308 brass. 223 brass also get hotter in the firing process, to the point that it will stick to the mesh on a brass catcher.

That article specifically says that cases are different though, and not just for 223 vs 5.56 NATO but for all cases in general.

Lots of other factors like Wylde vs Match vs other chambers.

In regard to the OP's question, "Is 5.56 and. 223 brass interchangeable or do they need to be segregated?", after reading that link I would have to say absolutely not treated the same, and even same caliber different headstamp should not be treated the same.

[SonofWWIIDI]

I just got hit by the deja vu train here. I hope that is just a memory of another thread from last year instead of my mind going...oh, look, squirrel!