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5.56 VS .223 Ammunition and Chamber Dimensions


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#1 OFFLINE   marsche

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Posted Nov. 27 2007 - 03:39 PM

There always seems to be a lot of confusion over the difference between a .223 and a 5.56 chamber. Is it safe to shoot this? Is it safe to do that? More confusion is added when some manufacturers advertise rifles with .223/5.56 chambers. I found this 'excellent' explaination on Wikipedia (http://en.wikipedia..../.223_Remington) and wanted to share it on this forum.

The .223 Remington is a sporting cartridge with the same external dimensions as the 5.56x45mm NATO military cartridge. It is loaded with a .224" diameter, jacketed bullet, with weights ranging from 40 up to 90 grains, though the most common loadings by far are 55 grains.

The primary difference between .223 Remington and 5.56 x 45 mm is that .223 is loaded to lower pressures and velocities compared to 5.56 mm. .223 Remington ammunition can be safely fired in a 5.56 mm chambered gun, but the reverse can be an unsafe combination. The additional pressure created by 5.56 mm ammo will frequently cause over-pressure problems such as difficult extraction, flowing brass, or popped primers, but in extreme cases, could damage or destroy the rifle. Chambers cut to .223 Remington specifications have a shorter leade (throat) area as well as slightly shorter headspace dimensions compared to 5.56 mm "military" chamber specs, which contributes to the pressure issues.

While the 5.56 mm and .223 cartridges are very similar, they are not identical. Military cases are made from thicker brass than commercial cases, which reduces the powder capacity (an important consideration for handloaders), and the NATO specification allows a higher chamber pressure. Test barrels made for 5.56mm NATO measure chamber pressure at the case mouth, as opposed to the SAAMI location. This difference accounts for upwards of 20,000+ psi difference in pressure measurements. That means that advertised pressure of 58,000 psi for 5.56mm NATO, is around 78,000 psi tested in .223 Rem test barrels (SAAMI .223 Rem Proof MAP is 78,500 psi so every 5.56mm round fired is a proof load, very dangerous). The 5.56 mm chambering, known as a NATO or mil-spec chambers, have a longer leade, which is the distance between the mouth of the cartridge and the point at which the rifling engages the bullet. The .223 chambering, known as the "SAAMI chamber", is allowed to have a shorter leade, and is only required to be proof tested to the lower SAAMI chamber pressure. To address these issues, various proprietary chambers exist, such as the Wylde chamber[2] or the Armalite chamber, which are designed to handle both 5.56 mm and .223 equally well.

Using commercial .223 cartridges in a 5.56-chambered rifle should work reliably, but generally will not be as accurate as when fired from a .223-chambered gun due to the excessive leade. [3] Using 5.56 mil-spec cartridges (such as the M855) in a .223-chambered rifle can lead to excessive wear and stress on the rifle and even be unsafe, and the SAAMI recommends against the practice.[4] Some commercial rifles marked as ".223 Remington" are in fact suited for 5.56 mm, such as many commercial AR-15 variants and the Ruger Mini-14, but the manufacturer should always be consulted to verify that this is acceptable before attempting it, and signs of excessive pressure (such as flattening or gas staining of the primers) should be looked for in the initial testing with 5.56 mm ammunition.

Edited by marsche, Nov. 27 2007 - 03:42 PM.



#2 Guest_fullyauto_*

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Posted Dec. 12 2007 - 06:47 PM

There always seems to be a lot of confusion over the difference between a .223 and a 5.56 chamber. Is it safe to shoot this? Is it safe to do that? More confusion is added when some manufacturers advertise rifles with .223/5.56 chambers. I found this 'excellent' explaination on Wikipedia (http://en.wikipedia..../.223_Remington) and wanted to share it on this forum.

The .223 Remington is a sporting cartridge with the same external dimensions as the 5.56x45mm NATO military cartridge. It is loaded with a .224" diameter, jacketed bullet, with weights ranging from 40 up to 90 grains, though the most common loadings by far are 55 grains.

The primary difference between .223 Remington and 5.56 x 45 mm is that .223 is loaded to lower pressures and velocities compared to 5.56 mm. .223 Remington ammunition can be safely fired in a 5.56 mm chambered gun, but the reverse can be an unsafe combination. The additional pressure created by 5.56 mm ammo will frequently cause over-pressure problems such as difficult extraction, flowing brass, or popped primers, but in extreme cases, could damage or destroy the rifle. Chambers cut to .223 Remington specifications have a shorter leade (throat) area as well as slightly shorter headspace dimensions compared to 5.56 mm "military" chamber specs, which contributes to the pressure issues.

While the 5.56 mm and .223 cartridges are very similar, they are not identical. Military cases are made from thicker brass than commercial cases, which reduces the powder capacity (an important consideration for handloaders), and the NATO specification allows a higher chamber pressure. Test barrels made for 5.56mm NATO measure chamber pressure at the case mouth, as opposed to the SAAMI location. This difference accounts for upwards of 20,000+ psi difference in pressure measurements. That means that advertised pressure of 58,000 psi for 5.56mm NATO, is around 78,000 psi tested in .223 Rem test barrels (SAAMI .223 Rem Proof MAP is 78,500 psi so every 5.56mm round fired is a proof load, very dangerous). The 5.56 mm chambering, known as a NATO or mil-spec chambers, have a longer leade, which is the distance between the mouth of the cartridge and the point at which the rifling engages the bullet. The .223 chambering, known as the "SAAMI chamber", is allowed to have a shorter leade, and is only required to be proof tested to the lower SAAMI chamber pressure. To address these issues, various proprietary chambers exist, such as the Wylde chamber[2] or the Armalite chamber, which are designed to handle both 5.56 mm and .223 equally well.

Using commercial .223 cartridges in a 5.56-chambered rifle should work reliably, but generally will not be as accurate as when fired from a .223-chambered gun due to the excessive leade. [3] Using 5.56 mil-spec cartridges (such as the M855) in a .223-chambered rifle can lead to excessive wear and stress on the rifle and even be unsafe, and the SAAMI recommends against the practice.[4] Some commercial rifles marked as ".223 Remington" are in fact suited for 5.56 mm, such as many commercial AR-15 variants and the Ruger Mini-14, but the manufacturer should always be consulted to verify that this is acceptable before attempting it, and signs of excessive pressure (such as flattening or gas staining of the primers) should be looked for in the initial testing with 5.56 mm ammunition.

This is one of the best explained articles on this subject I have seen, so many people do confuse this and one thing that I think you said which to me is one of the most important things is powder capacity in military brass vs commercial brass that was a very critical point for us reloaders. thanks for the awsome info explained wonderfully.


#3 OFFLINE   SAXD40

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Posted Jun. 11 2010 - 07:05 PM

There always seems to be a lot of confusion over the difference between a .223 and a 5.56 chamber. Is it safe to shoot this? Is it safe to do that? More confusion is added when some manufacturers advertise rifles with .223/5.56 chambers. I found this 'excellent' explaination on Wikipedia (http://en.wikipedia..../.223_Remington) and wanted to share it on this forum.

The .223 Remington is a sporting cartridge with the same external dimensions as the 5.56x45mm NATO military cartridge. It is loaded with a .224" diameter, jacketed bullet, with weights ranging from 40 up to 90 grains, though the most common loadings by far are 55 grains.

The primary difference between .223 Remington and 5.56 x 45 mm is that .223 is loaded to lower pressures and velocities compared to 5.56 mm. .223 Remington ammunition can be safely fired in a 5.56 mm chambered gun, but the reverse can be an unsafe combination. The additional pressure created by 5.56 mm ammo will frequently cause over-pressure problems such as difficult extraction, flowing brass, or popped primers, but in extreme cases, could damage or destroy the rifle. Chambers cut to .223 Remington specifications have a shorter leade (throat) area as well as slightly shorter headspace dimensions compared to 5.56 mm "military" chamber specs, which contributes to the pressure issues.

While the 5.56 mm and .223 cartridges are very similar, they are not identical. Military cases are made from thicker brass than commercial cases, which reduces the powder capacity (an important consideration for handloaders), and the NATO specification allows a higher chamber pressure. Test barrels made for 5.56mm NATO measure chamber pressure at the case mouth, as opposed to the SAAMI location. This difference accounts for upwards of 20,000+ psi difference in pressure measurements. That means that advertised pressure of 58,000 psi for 5.56mm NATO, is around 78,000 psi tested in .223 Rem test barrels (SAAMI .223 Rem Proof MAP is 78,500 psi so every 5.56mm round fired is a proof load, very dangerous). The 5.56 mm chambering, known as a NATO or mil-spec chambers, have a longer leade, which is the distance between the mouth of the cartridge and the point at which the rifling engages the bullet. The .223 chambering, known as the "SAAMI chamber", is allowed to have a shorter leade, and is only required to be proof tested to the lower SAAMI chamber pressure. To address these issues, various proprietary chambers exist, such as the Wylde chamber[2] or the Armalite chamber, which are designed to handle both 5.56 mm and .223 equally well.

Using commercial .223 cartridges in a 5.56-chambered rifle should work reliably, but generally will not be as accurate as when fired from a .223-chambered gun due to the excessive leade. [3] Using 5.56 mil-spec cartridges (such as the M855) in a .223-chambered rifle can lead to excessive wear and stress on the rifle and even be unsafe, and the SAAMI recommends against the practice.[4] Some commercial rifles marked as ".223 Remington" are in fact suited for 5.56 mm, such as many commercial AR-15 variants and the Ruger Mini-14, but the manufacturer should always be consulted to verify that this is acceptable before attempting it, and signs of excessive pressure (such as flattening or gas staining of the primers) should be looked for in the initial testing with 5.56 mm ammunition.


See this page http://www.cheaperthandirt.com/MediaPages/ArticleDetail.aspx?mediaid=316 ... It seems to me that mr. Marsche is very good at the copy and paste feature... Nice work..........


#4 OFFLINE   AnonymousD

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Posted Jun. 11 2010 - 07:26 PM

See this page http://www.cheaperthandirt.com/MediaPages/ArticleDetail.aspx?mediaid=316 ... It seems to me that mr. Marsche is very good at the copy and paste feature... Nice work..........

He never said he wrote it. He said he found it online.


#5 OFFLINE   GLShooter

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Posted Jun. 11 2010 - 07:33 PM

He never said he wrote it. He said he found it online.


Kind of like a Bible, lots of printers but still the good word.

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#6 ONLINE   FrostyBullet

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Posted Jun. 14 2010 - 10:57 AM

I can't seem to find any reloading / handloading data on the .556 round, where there is a multitude of data on the .223.

Several calls to companies like Sierra, seem to think the .556 and .223 are identical "just load the same as the .223" is the standard answer from them, although a call to Hornady seemed to find someone knowledgeable about the differences.

This does not account for higher pressures although I understand NATO and SAAMI use difference testing positions when measuring pressures.

After shooting several cases of .556 and .223 I can tell a noticeable difference, in recoil, accuracy, etc., just the recoil alone does not account for a possible heavier or lighter grain bullet as is mentioned by some, the .556 is definitely a hotter round.

So where can one go to find some accurate handloading data on the .556?


#7 OFFLINE   Pepper

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Posted Jun. 14 2010 - 11:16 AM

See this page http://www.cheaperthandirt.com/MediaPages/ArticleDetail.aspx?mediaid=316 ... It seems to me that mr. Marsche is very good at the copy and paste feature... Nice work..........

Given the reputation CTD has, I doubt anyone went there for information. Also given their business practices, it wouldn't surprise me if they ripped it off from Wikipedia and passed it off as their own work.


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#8 ONLINE   GLShooter

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Posted Jun. 14 2010 - 11:57 AM

I can't seem to find any reloading / handloading data on the .556 round, where there is a multitude of data on the .223.

Several calls to companies like Sierra, seem to think the .556 and .223 are identical "just load the same as the .223" is the standard answer from them, although a call to Hornady seemed to find someone knowledgeable about the differences.

This does not account for higher pressures although I understand NATO and SAAMI use difference testing positions when measuring pressures.

After shooting several cases of .556 and .223 I can tell a noticeable difference, in recoil, accuracy, etc., just the recoil alone does not account for a possible heavier or lighter grain bullet as is mentioned by some, the .556 is definitely a hotter round.

So where can one go to find some accurate handloading data on the .556?


I have an feeling on this one and I could be all wrong but here it goes. No commercial reloading supplier works up loads for the 5.56. They are going to common denominator it for the 223 pressures. With the various case capacities of the military vs commercial brass they don't want guys feeding their rifles loads that would be "unsafe" in the 223 chambers by loading hot in the military case.

At least with the "crimped" primer you must do something to render the case reloadable for you to use in the 223. That "implies" you are at least cognizant of the "difference" to me.

The extra gained from running 5.56 pressures is not that noticeable. You can make some screamers in the 223 that will stay right up with the 5.56 through powder selection. The interesting thing, to me, about that is that many times those "screamers" will not run in an AR. The pressures are all wrong. They are basically bolt gun loads in many instances. I know my 20 Tactical was pretty darn picky on what I fed it and I used well over 60 different combinations learning about that.

Just my thoughts.

Greg


#9 ONLINE   FrostyBullet

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Posted Jun. 16 2010 - 07:32 PM

I have an feeling on this one and I could be all wrong but here it goes. No commercial reloading supplier works up loads for the 5.56. They are going to common denominator it for the 223 pressures. With the various case capacities of the military vs commercial brass they don't want guys feeding their rifles loads that would be "unsafe" in the 223 chambers by loading hot in the military case.


Reloading, in the hands of the generally stupid, is dangerous anyway. A standard disclaimer would cover their a**es.

I would think it would be more unsafe for those that want 5.56 rounds to experiment on their own, than to publish test data with a disclaimer. I did find someone at Hornady support that gave me some good info.

I also found some reload data at another site, but it requires paid membership to give out any info... :realmad:


#10 OFFLINE   VietVet

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Posted Jun. 20 2010 - 07:22 AM

Given the reputation CTD has, I doubt anyone went there for information. Also given their business practices, it wouldn't surprise me if they ripped it off from Wikipedia and passed it off as their own work.


+1 :thumb:


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#11 OFFLINE   The War Wagon

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Posted Jun. 20 2010 - 07:41 AM

HOLY thread resuscitation, Batman! :laugh:


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#12 OFFLINE   timosh

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Posted Jul. 25 2010 - 08:51 PM

This is an old message thread, but I'll see if anyone answers...

I purchased a RRA A4 Varmint upper with the WYLDE chamber, 1:8 twist. It LOVES 55gr. Ballistic tip ammo. However, I want to do some reloading for prairie poodles. I can't affort to purchase 1000+ rounds of commercial ammo.

However, nowhere can I find the exact dimensions for the Wylde chamber, and guidance for reloading dimensions. I sent an email to Redding asking for advice, and a technician replied that he had never heard of the Wylde chamber, and could not offer any advice!! :sad:

So, I guess the question is: How is reloading the Wylde chamber different from the .223 or the 5.56?
With the longer leade, is the case trim length different? ( .223 recommended 1.750) Wylde = ?

Any other changes? Any advise?

Thanks,

timosh


#13 OFFLINE   newbe

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Posted Jul. 27 2010 - 03:07 AM

Good Q. I've got two RRAs with the "Wylde" chambering. It's supposedly ok to shoot .223 and 5.56 without any issues. I believe it is slightly tighter than the 5.56 chamber but not as tight as the .223 (less lead)?

I think if you load to 5.56 (if that information is even avail), you'd be fine.

You could always call RRA to find out the specifics if they're willing to give out that info.


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#14 ONLINE   GLShooter

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Posted Jul. 27 2010 - 09:50 AM

This is an old message thread, but I'll see if anyone answers...

I purchased a RRA A4 Varmint upper with the WYLDE chamber, 1:8 twist. It LOVES 55gr. Ballistic tip ammo. However, I want to do some reloading for prairie poodles. I can't affort to purchase 1000+ rounds of commercial ammo.

However, nowhere can I find the exact dimensions for the Wylde chamber, and guidance for reloading dimensions. I sent an email to Redding asking for advice, and a technician replied that he had never heard of the Wylde chamber, and could not offer any advice!! :sad:

So, I guess the question is: How is reloading the Wylde chamber different from the .223 or the 5.56?
With the longer leade, is the case trim length different? ( .223 recommended 1.750) Wylde = ?

Any other changes? Any advise?

Thanks,

timosh


Just load up your ammo to standard 223 dimensions/data. A Wilde chamber is basically a long throated 223. It will alow you to shoot 5.56 in safety in your 223 and vice versa. Standard 2.260 COL and case lenght 1.750 will do it for you all day long. Remember you can always shoot regular 223 in a 5.56 chmaber without issue. It's when you cram that 5.56 cartridge up tight onto the throat and leade of the 223 that you hit pressures.

All your loading data you have in front of you (99.9% of the time) is going to be for 223 length ammo with 223 pressures and you will be fine with it.

Greg

Edited by GLShooter, Jul. 27 2010 - 09:51 AM.



#15 ONLINE   GLShooter

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Posted Jul. 27 2010 - 10:45 AM

Just load up your ammo to standard 223 dimensions/data. A Wilde chamber is basically a long throated 223. It will alow you to shoot 5.56 in safety in your 223 and vice versa. Standard 2.260 COL and case lenght 1.750 will do it for you all day long. Remember you can always shoot regular 223 in a 5.56 chmaber without issue. It's when you cram that 5.56 cartridge up tight onto the throat and leade of the 223 that you hit pressures.

All your loading data you have in front of you (99.9% of the time) is going to be for 223 length ammo with 223 pressures and you will be fine with it.

Greg


PS: If you want to see some down range actions on those prairie poodles load up the Hornady VMAX or the Nosler BT's in 40 grain with a stout charge and watch the action. You will be pleased with the results.


#16 ONLINE   kimbajmann

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Posted Feb. 08 2011 - 06:14 PM

I can't seem to find any reloading / handloading data on the .556 round, where there is a multitude of data on the .223.

Several calls to companies like Sierra, seem to think the .556 and .223 are identical "just load the same as the .223" is the standard answer from them, although a call to Hornady seemed to find someone knowledgeable about the differences.

This does not account for higher pressures although I understand NATO and SAAMI use difference testing positions when measuring pressures.

After shooting several cases of .556 and .223 I can tell a noticeable difference, in recoil, accuracy, etc., just the recoil alone does not account for a possible heavier or lighter grain bullet as is mentioned by some, the .556 is definitely a hotter round.

So where can one go to find some accurate handloading data on the .556?

my nosler reloading #6 has loadfs for 5.56 nato
in 69 grn cust comp, 77 grn and 80 grn. I will not list the loads here, but vel are ranging from 2957 - 2692 on the max pub loads for the range of bullets


#17 OFFLINE   kimbajmann

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Posted Feb. 08 2011 - 06:19 PM

my nosler reloading #6 has loadfs for 5.56 nato
in 69 grn cust comp, 77 grn and 80 grn. I will not list the loads here, but vel are ranging from 2957 - 2692 on the max pub loads for the range of bullets

same book has 60grn partition that fly at a max pub of 3219 their load with benchmark powder going around 3080 was indicated to be the most accurate, but that is out of a 1/12 twist rem 223 barrel, so you will have to play with it out of a standard 223 or nato 5.56 twist rate. the prev listed nato loads were out of a 20" 1/7 barrel.


#18 OFFLINE   CJohnson76

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Posted Feb. 08 2011 - 06:26 PM

:thumb:


#19 OFFLINE   AllRighty15

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Posted Feb. 10 2011 - 06:30 PM

I look at it like the 38 and 357mag ammo


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#20 OFFLINE   newbe

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Posted Feb. 10 2011 - 07:40 PM

I look at it like the 38 and 357mag ammo

Thats not even CLOSE to the same caliber....... :smartass:





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