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Dumbass question: 5.56MM and .223 chamberings. Am I getting this right? Login/Join 
Member
Picture of RichardC
posted
If a rifle is marked 5.56MM/.223 like older Colt AR's, it's safe to fire either cartridge but one might get better groups with best match quality factory made 5.56MM ammo?

If marked only .223, one should only use .223 marked 'match' ammo for safety and accuracy?

If it's marked 5.56MM like a Knight's Armament AR, one can safely fire factory match grade .223 and 5.6MM ammo but might get better accuracy from 5.56MM?


The Wylde chambers are understandable to me as an option in the future.


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Posts: 14384 | Location: Florida | Registered: June 23, 2003Reply With QuoteReport This Post
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Either work in a 5.56.

Only shoot 223 in a 223.

And yes accuracy suffers when shooting 223 from a 5.56.





12 years to retirement! Just waiting!
 
Posts: 5005 | Location: Maryland | Registered: August 10, 2009Reply With QuoteReport This Post
I swear I had
something for this
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quote:
Originally posted by OttoSig:
Only shoot 223 in a 223.


For American guns: Yes. Sometimes other countries will make their guns .223 because 5.56 is a "military" caliber. On those, there's some question.
 
Posts: 3044 | Location: Kansas City, MO | Registered: May 28, 2004Reply With QuoteReport This Post
Freethinker
Picture of sigfreund
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quote:
Originally posted by DanH:
Sometimes other countries will make their guns .223 because 5.56 is a "military" caliber. On those, there's some question.

Not suggesting for a moment that anyone else do it, but my Tikka T3 in 223 Remington handles IMI 77 grain 5.56 ammunition fine with no excess pressure signs.

And the question reminds me of something I’ve long pondered.

Most 5.56 ammunition purchased these days is undoubtedly fired in AR-style rifles, and the vast majority of such rifles are chambered for that cartridge. But there are still a substantial number of rifles like mine that are chambered for the 223 Remington cartridge, and I would bet a nickel that a significant number of owners of such rifles are not aware of the supposed danger of firing that cheap 5.56 stuff in their guns. When we think of the number of people who don’t get the word about other things that are even more obvious, that leads me to wonder why, if 5.56 in 223 is so dangerous, we don’t hear of its catastrophic consequences all the time—or at least once in a while. Hmm …?

(And yes, I’ve seen the videos and read the articles about the issue, and I believe I even understand them.)




7/93
 
Posts: 45885 | Location: 10,150 Feet Above Sea Level in Colorado | Registered: April 04, 2002Reply With QuoteReport This Post
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quote:
For American guns: Yes. Sometimes other countries will make their guns .223 because 5.56 is a "military" caliber.

I recall reading somewhere that outside of the U.S., .223REM is quite often regarded and loaded the same as 5.56x45. For instance, at least some of the labeled 55gr ".223" ammo loads out of Taiwan seem to shoot and recoil damn near identically to domestically sourced M193 5.56. I've thought the same about some of the .223-labeled European loads that I've shot in the past as well.


-MG
 
Posts: 1300 | Location: The commie, rainy side of WA | Registered: April 19, 2020Reply With QuoteReport This Post
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Picture of powermad
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quote:
Not suggesting for a moment that anyone else do it, but my Tikka T3 in 223 Remington handles IMI 77 grain 5.56 ammunition fine with no excess pressure signs.


5.56 does not equal 5.56 NATO.
5.56 NATO is the M855 with the SS109 projectile.
That is what they are referring to.
The shape of the bullet is what causes pressure spikes in some .223 Chambers.
The shape of the 5.56 NATO throat and leade
is what can make .223 erratic.

Lucky Gunner did a pretty good article with cool nerdy stuff to read the pressure.
While they didn't blow up a gun I can see why it's not a good idea.
 
Posts: 1140 | Location: Portland Oregon | Registered: October 01, 2011Reply With QuoteReport This Post
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Picture of RichardC
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quote:
Originally posted by powermad:


Lucky Gunner did a pretty good article with cool nerdy stuff to read the pressure.
While they didn't blow up a gun I can see why it's not a good idea.


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


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Posts: 14384 | Location: Florida | Registered: June 23, 2003Reply With QuoteReport This Post
Freethinker
Picture of sigfreund
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quote:
Originally posted by powermad:
5.56 NATO is the M855 with the SS109 projectile.

I have been following this sort of thing for a long time, and that’s the first I’ve ever seen that statement.

If I understand correctly, then, you are saying that there is only one specific 5.56mm load that 223 Remington shooters need to avoid—yes?




7/93
 
Posts: 45885 | Location: 10,150 Feet Above Sea Level in Colorado | Registered: April 04, 2002Reply With QuoteReport This Post
Little ray
of sunshine
Picture of jhe888
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quote:
Originally posted by sigfreund:
quote:
Originally posted by DanH:
Sometimes other countries will make their guns .223 because 5.56 is a "military" caliber. On those, there's some question.

Not suggesting for a moment that anyone else do it, but my Tikka T3 in 223 Remington handles IMI 77 grain 5.56 ammunition fine with no excess pressure signs.

And the question reminds me of something I’ve long pondered.

Most 5.56 ammunition purchased these days is undoubtedly fired in AR-style rifles, and the vast majority of such rifles are chambered for that cartridge. But there are still a substantial number of rifles like mine that are chambered for the 223 Remington cartridge, and I would bet a nickel that a significant number of owners of such rifles are not aware of the supposed danger of firing that cheap 5.56 stuff in their guns. When we think of the number of people who don’t get the word about other things that are even more obvious, that leads me to wonder why, if 5.56 in 223 is so dangerous, we don’t hear of its catastrophic consequences all the time—or at least once in a while. Hmm …?

(And yes, I’ve seen the videos and read the articles about the issue, and I believe I even understand them.)


Because damn near all rifles chambered in .223 can handle 5.56. The difference is small enough that the problem is largely theoretical. It may have some effect on accuracy, but most people don't even shoot well enough to notice that.

If you shoot 5.56 in your .223, check any given load for signs of excess pressure. You probably won't see any, but if you do, don't shoot any more. It almost certainly won't blow up your gun. It would take a .223 chamber and leade on the tighest end of the spectrum and .556 ammo on the highest pressure end of that spectrum to cause a catastrophe.




The fish is mute, expressionless. The fish doesn't think because the fish knows everything.
 
Posts: 51787 | Location: Texas | Registered: February 10, 2004Reply With QuoteReport This Post
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Picture of powermad
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quote:
Originally posted by sigfreund:
quote:
Originally posted by powermad:
5.56 NATO is the M855 with the SS109 projectile.

I have been following this sort of thing for a long time, and that’s the first I’ve ever seen that statement.


If I understand correctly, then, you are saying that there is only one specific 5.56mm load that 223 Remington shooters need to avoid—yes?


Yep, there is only one 5.56 NATO, the M855 or equivalent with the SS109 pill.
 
Posts: 1140 | Location: Portland Oregon | Registered: October 01, 2011Reply With QuoteReport This Post
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I’ve seen on two occasions AR’s with .223 chambers, blowing primers and having extraction issues firing 5.56 ammo.


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Posts: 19833 | Location: 18th & Fairfax  | Registered: May 17, 2003Reply With QuoteReport This Post
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quote:
Originally posted by RichardC:
If a rifle is marked 5.56MM/.223 like older Colt AR's, it's safe to fire either cartridge but one might get better groups with best match quality factory made 5.56MM ammo?

Accuracy depends on the barrel and the ammo.

I have multiple 5.56-labeled Wilson Combat barrels and one 5.56-labeled DCM barrel. I've shot a variety of factory ammo through them, both 5.56 and 223. It is challenging to find 5.56 match ammo, especially when trying to compare an apples-to-apples bullet type. I've seen the much of the 5.56 factory ammo uses FMJ 55 and 62 grain bullets. Black Hills and Hornady are among the few companies offering match 5.56 loads with heavier bullets. What I've experienced:
- Factory 5.56 loads tend to produce a little faster MV than their 223 versions. Can be as much as 200 fps difference. SDs were comparable for both 5.56 and 223 loads.
- The best 5-round groups at 100 yards from the 5.56 were comparable to the 223 versions. The worst groups were pretty much always from the 5.56 ammo. The average group sizes were smaller with 223 ammo.
- As target distances increased, most 5.56 loads' accuracy deteriorated noticeably. In the 250-350 yard ballpark, none of the 5.56 loads I tried could hang with comparable 223 loads.

In steel matches that use AR15 rifles, competitors have both 5.56 and 223 labeled barrels. For guys who use FMJ 55 and 62 grain ammo, I don't recall any differences in one barrel versus the other -- they lack accuracy at distance. I know guys who shoot their 5.56 barrels very accurately, but they hand load and use 69-77 grain bullets.
 
Posts: 7400 | Location: Colorado | Registered: January 26, 2008Reply With QuoteReport This Post
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Picture of powermad
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For 5.56 match type ammo the Mk262 seems to be the standard but I have never been able to find any.

A few do make a clone like the IMI Razor core using the same 77 gr SMK
I picked up 500 of the Sellier and Bellot 5.56, 77 gr to try out, not a SMK but their own OTM bullet.
Not much for reviews on it but for $.84 ea I'll give it a try, IMI was going for $1.05 ea.
I've used a few different S&B pistol rounds with no complaints.
Doesn't look bad on paper and I do like that they give all the relevant info on the package instead of scouring the internet for it.

About 100 more MV over 77gr FGMM.
No sealant but the primer is crimped and the brass is annealed.

I have a bit of the Mk318 mod1 that uses a 62gr OTM over the penetrator, only tried that out at 50 yds so no data on longer range accuracy but it looks to be about the same as 855, maybe a bit better groups.
 
Posts: 1140 | Location: Portland Oregon | Registered: October 01, 2011Reply With QuoteReport This Post
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quote:
Originally posted by powermad:
quote:
Originally posted by sigfreund:
quote:
Originally posted by powermad:
5.56 NATO is the M855 with the SS109 projectile.

I have been following this sort of thing for a long time, and that’s the first I’ve ever seen that statement.


If I understand correctly, then, you are saying that there is only one specific 5.56mm load that 223 Remington shooters need to avoid—yes?


Yep, there is only one 5.56 NATO, the M855 or equivalent with the SS109 pill.



I learned something today too.

https://military-history.fando...n%2DNATO%20countries Scroll down to performance.

"The 5.56×45mm NATO cartridge with the standard 62 gr. steel core bullets (NATO: SS109; U.S.: M855)"


 
Posts: 5122 | Location: Pittsburgh, PA, USA | Registered: February 27, 2001Reply With QuoteReport This Post
fugitive from reality
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quote:
Originally posted by jhe888:
If you shoot 5.56 in your .223, check any given load for signs of excess pressure. You probably won't see any, but if you do, don't shoot any more. It almost certainly won't blow up your gun. It would take a .223 chamber and leade on the tighest end of the spectrum and .556 ammo on the highest pressure end of that spectrum to cause a catastrophe.


I have personally fired actual USGI M855 out of match grade .223 remington chambers. All I got was a slight flattening of the primers. I would not try this on a 90+ degrie day, but like jhe888 said, it's an extreme condition that's very hard to duplicate.


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Posts: 7026 | Location: Newyorkistan | Registered: March 28, 2007Reply With QuoteReport This Post
semi-reformed sailor
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Just to add some confusion to the mix. The “NATO” 5.56 round is/was the M193 55grain FMJ lead core bullet. This round has been replaced by the M855.

Units began depleting their stock piles of M193 since M855 was introduced. But some NG units still have it and the CG has piles of it that are just used for training now.

But technically, the nato round is now M855 steel penetrator 62 grain bullet.



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“You may beat me, but you will never win.” sigmonkey-2020

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Posts: 9983 | Location: Temple, Texas! | Registered: October 07, 2006Reply With QuoteReport This Post
Freethinker
Picture of sigfreund
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quote:
Originally posted by MikeinNC:
Just to add some confusion to the mix. The “NATO” 5.56 round is/was the M193 55grain FMJ lead core bullet.

Ah, something I didn’t think about earlier.
Does that mean until the M855 cartridge came along that it was unsafe to shoot M193 ammunition in 223 Remington chambers because it was the prohibited NATO round, but as soon as it was declared to not be the NATO cartridge, it suddenly, ipso facto, became safe? If something like the M855A1 becomes the official NATO cartridge, will that mean all the hoarded ordinary M855 will be good to shoot in 223 chambers? Confused

That seems to be what some would have us believe. Or maybe not. Roll Eyes




7/93
 
Posts: 45885 | Location: 10,150 Feet Above Sea Level in Colorado | Registered: April 04, 2002Reply With QuoteReport This Post
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posted Hide Post
quote:
Originally posted by jhe888:
quote:
Originally posted by sigfreund:
quote:
Originally posted by DanH:
Sometimes other countries will make their guns .223 because 5.56 is a "military" caliber. On those, there's some question.

Not suggesting for a moment that anyone else do it, but my Tikka T3 in 223 Remington handles IMI 77 grain 5.56 ammunition fine with no excess pressure signs.

And the question reminds me of something I’ve long pondered.

Most 5.56 ammunition purchased these days is undoubtedly fired in AR-style rifles, and the vast majority of such rifles are chambered for that cartridge. But there are still a substantial number of rifles like mine that are chambered for the 223 Remington cartridge, and I would bet a nickel that a significant number of owners of such rifles are not aware of the supposed danger of firing that cheap 5.56 stuff in their guns. When we think of the number of people who don’t get the word about other things that are even more obvious, that leads me to wonder why, if 5.56 in 223 is so dangerous, we don’t hear of its catastrophic consequences all the time—or at least once in a while. Hmm …?

(And yes, I’ve seen the videos and read the articles about the issue, and I believe I even understand them.)


Because damn near all rifles chambered in .223 can handle 5.56. The difference is small enough that the problem is largely theoretical. It may have some effect on accuracy, but most people don't even shoot well enough to notice that.

If you shoot 5.56 in your .223, check any given load for signs of excess pressure. You probably won't see any, but if you do, don't shoot any more. It almost certainly won't blow up your gun. It would take a .223 chamber and leade on the tighest end of the spectrum and .556 ammo on the highest pressure end of that spectrum to cause a catastrophe.


I agree. I've shot 5.56 in several 223 bolt action rifles and never seen any pressure issues. I'm not saying it can't happen, but it's never been an issue for me.
 
Posts: 867 | Location: WV | Registered: May 30, 2013Reply With QuoteReport This Post
I Deal In Lead
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quote:
Originally posted by jhe888:
Because damn near all rifles chambered in .223 can handle 5.56. The difference is small enough that the problem is largely theoretical. It may have some effect on accuracy, but most people don't even shoot well enough to notice that.

If you shoot 5.56 in your .223, check any given load for signs of excess pressure. You probably won't see any, but if you do, don't shoot any more. It almost certainly won't blow up your gun. It would take a .223 chamber and leade on the tighest end of the spectrum and .556 ammo on the highest pressure end of that spectrum to cause a catastrophe.


You're right but I'm sure the safety police will be along soon to tell us how wrong you are.
 
Posts: 9636 | Location: Gilbert Arizona | Registered: March 21, 2013Reply With QuoteReport This Post
quarter MOA visionary
Picture of smschulz
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quote:
Because damn near all rifles chambered in .223 can handle 5.56.
The difference is small enough that the problem is largely theoretical.


I only shoot Wylde chambers for the most part and never had any issues with any ammo.
I mostly will reload for accuracy reasons though.
On the other hand > AR10 ammo is an entirely different animal and what my bolt action can shoot > my AR10's cannot handle (pressure issues).
 
Posts: 20760 | Location: Houston, TX | Registered: June 11, 2006Reply With QuoteReport This Post
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