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Old September 21, 2018, 09:02 AM   #1
joeranger
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New NRA explanation of .223 vs 5.56, examples?

Oh look, a dead horse, let's beat it
I just read an overly detailed explanation of 223 vs 5.56.
https://www.americanrifleman.org/art...CENSORED-=0918

Summary, dangerous to fire 5.56 in a 223, less accurate to fire 223 in a 5.56.

Does anyone here have any examples or experience with either of these two issues? Has a 223 AR exploded with 5.56 or have the 223 rounds gone off in random directions in a 5.56? (Obviously, if the rounds are not matched to the barrel for weight and twist, there will be a difference in accuracy)

Just curious if there are any interesting stories...
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Old September 21, 2018, 11:22 AM   #2
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Yes, my Remington .223 VS had a severe case head failure shooting 55 grain FMJ 5.56 Malaysian ammo. My .223 TC barrel would not even chamber a 62 grain greentip.

I would not worry about that in any semi auto, no matter what it is marked, unless it's .222!~
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Old September 21, 2018, 11:36 AM   #3
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We had a handfull of examples when 556 ammo blew out primers in 223 guns. BUT, that was in extreamly hot conditions (Nevada desert in the summer).

No harm done. The big issue is one of those loose primers falling into the trigger group and causing problems.
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Old September 21, 2018, 03:29 PM   #4
Jim567
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My Savage .223 has never shown signs of high pressure shooting 5.56.
For what it is worth.
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Old September 21, 2018, 04:59 PM   #5
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The article greatly over-simplifies most of the points it touches on, and ignores a few other important points. One point ignored is the fact that probably no civilian AR-15s are ever chambered for .223 Remington. My understanding is that, at least in years past, AR-15s were mostly chambered in a hybrid of the two, called the Wylde chamber.

https://en.wikipedia.org/wiki/.223_Wylde_chamber

Another point glossed over is that there are other barrel twist rates than 1:12 and 1:7. My AR-15 carbine has a 1:9 twist. At the time I bought it, this was by far the most common twist rate for AR-15s, and it's more than adequate for 62-grain bullets, and probably up to about 70-grain. The 1:7 twist rate only came about fairly recently, as the military (and long range civilian shooters) began shooting bullets heavier than 70 grains, with commensurately longer bullet lengths.

Lastly, even the ,223 Remington chamber is safe for use with the original 55-grain 5.56x45 ammunition. Where it becomes marginal is, as the Wikipedia article explains, when the 62-grain 5.56x45 cartridge was adopted.

All in all, this is a very disappointing effort on the part of American Rifleman.
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Old September 21, 2018, 07:28 PM   #6
JohnKSa
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Quote:
Summary, dangerous to fire 5.56 in a 223, less accurate to fire 223 in a 5.56.
"Dangerous" probably isn't exactly the right term. There is some potential, particularly when there's another contributor (such as very hot weather) for the mismatch to cause problems like popped primers.

Here's a pretty thorough treatment of the topic.

https://thefiringline.com/forums/sho...d.php?t=530912
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Old September 21, 2018, 08:53 PM   #7
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The answer is a barrel chambered in .223 Wylde. Shoots both safely and accurately.
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Old September 21, 2018, 10:26 PM   #8
Aguila Blanca
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If you want the whole story on the .223 Remington / 5.56x45, I don't think there's a better explanation of the whole enchilada than the Ammo Oracle:

https://www.ar15.com/ammo-oracle/
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Old September 22, 2018, 07:48 AM   #9
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The NRA simply parroted SAAMI.

In 1968 i re-chambered a .222 Sako to .223 Remington in order to shoot US military 5.56mm ammunition. i've fired untold thousands M193 ball rounds in .223 chambers with no problems.

There are at least one dozen different .223/5.56mm chambers. Contrary to popular belief not all chambering operations are accomplished by gunsmiths. In many cases chamber dimensions depend on the person wielding the reamer.

https://www.luckygunner.com/labs/5-56-vs-223/

Do not attempt to fire 5.56mm in a tight .223 match chamber. The round will most likely not chamber anyway.

There is a problem with some of the US made 5.56mm military ammo currently being sold. Some case necks are very long.

If you don't feel good about shooting 5.56mm military ammo in a .223 chamber then don't do it.
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Old September 23, 2018, 04:30 AM   #10
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My cz527 does not shoot 556, well it shoots it but they keyhole

My tikka shoots them but no accuracy to write about
Cheapest 223 shots under Moa anyway so no need

And I can use that brass to reloading
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Old September 23, 2018, 06:04 AM   #11
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My CZ 527 shoots M193 55 grain military ball very well: Not so the 62 grain M855.
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Old September 23, 2018, 09:47 AM   #12
Aguila Blanca
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Quote:
Originally Posted by thallub
My CZ 527 shoots M193 55 grain military ball very well: Not so the 62 grain M855.
What's the twist rate for the CZ 527?

CZ's specs say it's 1:9. That should handle 62-grain M855 okay. Are the specs wrong, or have they changed?

http://cz-usa.com/product/cz-527-carbine-223-rem/
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Old September 23, 2018, 06:27 PM   #13
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At the time my CZ527 was purchased only the Varmint model came with 1/9" twist rate. Mine is 1/12" twist.

The M855 bullets don't keyhole at 125 yards. They just make awful groups.
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Old September 23, 2018, 06:54 PM   #14
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At 1:12 twist, you're going to be limited to lead core, copper-jacketed bullets. Just about anything with a steel core or made of solid copper is going to be too long to stabilize.

With lead core, copper-jacketed bullets, if you keep it to 60gr and under, you should have no trouble. You can probably push the boundaries a little, especially with a longer barrel and if you're not trying to shoot a long way past 100 yards.
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Old September 26, 2018, 07:12 PM   #15
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Yes

Yes, years ago, I personally fired m193, possibly m855 (my memory fades), in a .223 chambered bolt action rifle, the first round was harder than normal to extract after firing, like a dummy, I fired another. The second round locked up the bolt action pretty tight. I took it to a gun smith and he was able to get it open and extracted, his diagnosis was too much pressure.

This was before the military ammunition "ban" and it was actual military surplus ammo and not "XM".

I believe it's probably a small percentage of 5.56 ammunition and .223 chamber combinations that will cause unsafe pressures, but I don't fire anyting 5.56 in a commercial .223 chamer at all now.

Additionally, I will always advise against firing 5.56 ammunition in a .223 chamber for liability reasons, I don't care if anone does it, but I sure didn't tell anyone it was OK to do.
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Old September 26, 2018, 11:35 PM   #16
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Interesting comment in an article I read recently. They were doing an interview with one of the folks who runs Black Hills ammo who mentioned that BH loads .223 and 5.56 to different pressure and doesn't recommend using their 5.56 ammo in .223 guns.
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Old September 27, 2018, 08:20 AM   #17
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I thought this was mostly an ancient matter that has no real practical relevance in the last 20 years or so. At least I have not worried about it at all over the last 20 years. I do happen to have an older Remington 788 bolt action rifle - perhaps I won't be shooting any of the green-tip stuff in that.
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Old September 29, 2018, 11:25 AM   #18
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You will find far more examples of factory 30-06 ammo having issues in rifles chambered in 30-06 than you'll find when firing 5.56 ammo in 223 chambers.
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Old September 29, 2018, 06:40 PM   #19
Don Dayacetah
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The most accurate rifle I own, shoots .75 MOA at 100 yards. Uses 50 grain .223
from a 1:7 - 5.56 bull barrel. Not inaccurate by my standards.
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