223 Load Data vs 556

A

akinswi

New member
I ran across this article

https://ultimatereloader.com/2018/08/05/223-vs-5-56-facts-and-myths/

Here is the section im interested in.


“Load data for 223 Remington and 5.56 NATO is not the same! Use the appropriate load data for the case you are loading.”

If the cases are within 1% dimensionally and you use the same bullet profile. why would the load data not be interchangeable?

From what I gathered from the article , the main difference between the two is the free bore in the firearm itself and not the actual cartridge. he pointed out specifically the 64 grain tracer rd and it’s different shape vs XM193 or 55FMJ bullet.

So if I use a standard 55FMJ in 223 case. Why Couldn’t you use 556 load data?
 
I

Ike Clanton

New member
As I understand it the brass isn’t the issue the rifles chamber and pressure rating is but I’ll leave this up to the experts.
 
A

akinswi

New member
In the article the pressure diff was 55,000 compared to 55114 so almost identical.

But yes Im waiting on what the experts say.

Because I don’t understand how a 223 bolt action rifle chamber couldn’t withstand the same pressure as an AR15 chamber.
 
J

JohnKSa

Administrator
There are some posts in the thread in the link that talk about the issue.

https://thefiringline.com/forums/showthread.php?t=530912

The only negative reports I've ever seen from the mismatch (5.56 in a .223 chamber) usually occur with an additional complicating factor (e.g. high ambient heat, a very dirty chamber) and the effect seems to be limited to blown/pierced primers, difficult extraction, etc.

It's not a "Don't do this or you'll blow up your gun for sure!" type deal, it's more of a "This could cause some issues that you would rather avoid so you might want to be aware of it." type deal.

Just out of curiosity, are you really having difficulty finding .223 loading data for 55gr FMJ bullets?
 
T

tangolima

New member
I have seen the article before. Reading it again carefully, one thing is new to me.

.223 Remington has 3 headspace gauges: go, no-go, and field. 5.56 NATO has 2; min and max. I suppose 5.56 NATO has acceptable headspace between 1.4636" to 1.4736" (between min & max), whereas .223 Remington is 1.4636" to 1.4666" (between go and no-go).

Does that mean a 5.56 NATO round may not even be chambered in a .223 Remington chamber? Or a .223 Remington round chambered in 5.56 NATO chamber will have excessive head clearance?

-TL

Sent from my SM-N960U using Tapatalk
 
T

tangolima

New member
After more digging, I think I have found answer to my own question.

Manufactured .223 Rem and 5.56 NATO ammo has the same dimension. The head to datum length is 1.4666" +0"-0.007". So there should never be chambering issue for factory ammo in either chamber.

However similar question remains. How do armorers check 5.56 NATO chambers? They use min and max gauges. It is therefore possible and acceptable for 5.56 NATO be longer than .223 Remington chamber. Normally it is non-issue. But for a handloader it may become a head scratcher. It is actually my own experience.

My first AR has 5.56 NATO chamber. I sized the brass to have head clearance of 0.003" - 0.005". My second AR has a Wylde chamber. The sized brass couldn't be chambered unless I sized them 0.003" shorter. Obviously the 5.56 NATO chamber was cut a bit longer than the Wylde chamber. The shortened brass in the 5.56 NATO chamber have head clearance up to 0.008". It is on the excessive side, but it hasn't caused any real trouble. I have never had any head separation. Brass die of split neck first.

-TL

Sent from my SM-P610 using Tapatalk
 
R

Recycled bullet

New member
556 is supposed to have a slightly deeper throat as compared against the barrel of a 223. How much deeper I don't know. The engineering reason for this may be to accommodate slightly heavier bullets and slightly higher pressure ammunition, and that all things else being equal 556 ammunition fired in a 556 gun will produce slightly less chamber pressure compared to 556 ammunition fired in a 223 chambered gun. Is it enough difference to make a difference I do not know.
 
H

HiBC

New member
Think about varmint weight bullets and .223 twist rates ,chamber details and bullet jump to rifling.
.223 shooters may be using 1 in 12 or 1 in 10 twist. bullet weights start about 40 gr, A 1 in 9 twist will work for 69 gr bullets.

As bullet weights went up for 5.56 sniping and match shooting, twists got tighter and magazine length loads go up to 77 gr. Single loaded rounds go up to 90 gr.
5.56 and Wylde chambers allow for more bullet length. Twist rates will be 1 in 9 or 1 in 8 or 1 in 7 typically. (Not ideal for 40 gr bullets)

Folks tend to overlook whether pressure is measured with cup,or cip (NATO?)or psi.

For about 50 years this has been discussed.

I wouldn't get excited about everything I saw on the internet. Even if its from somebody who calls himself "The Ultimate Reloader".

Yes,I tend to reference the Hornady "AR-15 5.56 Match Load" section of the manual. I tend to shoot 75 to 77 gr bullets. This section will show test results for correct powders to use with heavy bullets and tight twists.
At mag length 2.260, these bullets will be deep seated. That takes up a little powder space.

So the question is : Assume Winchester brass. New brass. Some headstamped .223 Rem. Some Headstamped 5.56 NATO.

Can one take a different level of pressure (safely) ? (Assuming same rifle)

If I'm loading 75 gr BTHP Hornady bullets using RE-15 and the mil spec CCI primers,COAL 2.260, to the published charge weights, is my AR-15 going to come all unglued (per The Ultimate Reloader?) if some .223 brass (gasp) is used?

I'd think there would be more variables in the mixed headstamps of WW vs FC, Prvi, PMC , Rem, Lapua,Norma, Hornady,etc. than between 5.56 vs .223 headstamp but I'm not the authority to say for sure.

I think maybe we have two different factory loads for two different applications.

Sort of like the .244 Remington vs 6mm Remington or the 280 Remington vs the 7mm Remington Express.


Regarding Tangolima's question on headspace gauges Go and No Go are used when building the rifle. The chamber is cut to depth or its not. Its a pass fail to sell as new. The "Field" guage tells us its worn out.

I assume the military max/min equate to the Go/No Go. Accept the rifle and pay for it. Thats qualify and purchase. I assume the "Field Gauge" is in the "Maintenance" dept. Its the "Worn out" gauge. Armorer tool vs purchasing tool.

FWIW,I get the idea that not too many home barreled AR-15 builds ever get a headspace gauge in their breech. Buy a barrel,buy a BCG, put them together?

I bought gauges. I use them.
 
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A

akinswi

New member
tangolima said:
After more digging, I think I have found answer to my own question.

Manufactured .223 Rem and 5.56 NATO ammo has the same dimension. The head to datum length is 1.4666" +0"-0.007". So there should never be chambering issue for factory ammo in either chamber.

However similar question remains. How do armorers check 5.56 NATO chambers? They use min and max gauges. It is therefore possible and acceptable for 5.56 NATO be longer than .223 Remington chamber. Normally it is non-issue. But for a handloader it may become a head scratcher. It is actually my own experience.

My first AR has 5.56 NATO chamber. I sized the brass to have head clearance of 0.003" - 0.005". My second AR has a Wylde chamber. The sized brass couldn't be chambered unless I sized them 0.003" shorter. Obviously the 5.56 NATO chamber was cut a bit longer than the Wylde chamber. The shortened brass in the 5.56 NATO chamber have head clearance up to 0.008". It is on the excessive side, but it hasn't caused any real trouble. I have never had any head separation. Brass die of split neck first.

-TL

Sent from my SM-P610 using Tapatalk
Click to expand...
Tang,

From what I understood from the article, the only difference in the two is more free bore clearance to allow different types of projectiles to be useed in the chamber of a M4 or M16 platform or stanard AR15, such as tracer rds.

But from What I gathered again from the article. I see no reason why you couldnt chamber a XM193 556 round in a bolt action 223.

Then again I maybe Im wrong, but I dont see where the science tells me I cant
 
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T

tangolima

New member
akinswi said:
Tang,



From what I understood from the article, the only difference in the two is more free bore clearance to allow different types of projectiles to be useed in the chamber of a M4 or M16 platform or stanard AR15, such as tracer rds.



But from What I gathered again from the article. I see no reason why you couldnt chamber a XM193 556 round in a bolt action 223.



Then again I maybe Im wrong, but I dont see where the science tells me I cant
Click to expand...
Correct if that round is factory (meets saami specs). May not work if it is a handload round with brass sized to fit a 5.56 NATO chamber.

-TL

Sent from my SM-N960U using Tapatalk
 
M

MarkCO

New member
First, the ask was about the difference in "load data" not chamber dimensions.

YES, there is a difference in load data. .223 Rem is 55Kpsi whereas 5.56x45NATO is 62,350Kpsi, gratned measured at difference locations. The internal case volume of NATO brass is also less by a small amount. Case head markings will tell you which is which.

Same powder, same bullet, same external dimensions, the .223 Rem load is not the same powder charge to produce the SAME pressure as the 5.56NATO load. Max loads for various powders are different as well. WHY they are different and why the ballistician stopped at that max load are due to several factors, many of which are not discernable to the hand-loader. Some faster powders, the 223Rem actually has a higher max load whereas with some slower powders, the 5.56NATO has the higher max load.
 
A

akinswi

New member
MarkCO said:
First, the ask was about the difference in "load data" not chamber dimensions.

YES, there is a difference in load data. .223 Rem is 55Kpsi whereas 5.56x45NATO is 62,350Kpsi, gratned measured at difference locations. The internal case volume of NATO brass is also less by a small amount. Case head markings will tell you which is which.

Same powder, same bullet, same external dimensions, the .223 Rem load is not the same powder charge to produce the SAME pressure as the 5.56NATO load. Max loads for various powders are different as well. WHY they are different and why the ballistician stopped at that max load are due to several factors, many of which are not discernable to the hand-loader. Some faster powders, the 223Rem actually has a higher max load whereas with some slower powders, the 5.56NATO has the higher max load.
Click to expand...
I didnt find a difference

223 Remington has the identical 62,366 psi (430.00 MPA)

556 has Maximum pressure (EPVAT) (430.00 MPA or 62,366 psi)

So if the case dimensions are the same so are the pressures why isnt the reloading data compatible.

Also the case volume is 1% less than 223 so less case volume to me sounds like a myth more than fact
 
4

44 AMP

Staff
A couple points to consider...

first, the "max pressure" being talked about and listed is the max allowable WORKING PRESSURE for the round. NOT the safety boundary or anywhere NEAR IT.

second, that pressure, (and all other cartridge specs) are set by whichever "umbrella" organization has jurisdiction over the ammo. In the US for commercial ammo, that is SAAMI. For govt ammo, its the milspec specification, set by the US govt (military) and in Europe its NATO.

Everybody has their own "kingdom" to rule, (and protect!) and everyone seems to use a different system for measuring pressure. Conversion between different systems produces different numbers even when the pressure measured is one constant thing.

Another point to consider is that "high pressure" and "dangerous" are not identical terms. High pressure covers everything even 1psi over the listed standard being used. Dangerous pressure is high pressure, but high pressure doesn't become dangerous until it approaches the mechanical safety limits of the materials and construction used.

80mph in a 55mph zone is high speed, but its not dangerous (assuming your vehicle and the road conditions are good) except to your wallet, generally.

The rounds are dimensionally the same. Both will fit and function is both rifles. One load may stress the other rifle SLIGHTLY more than allowed by the established standard being used, but not to a dangerous degree.

This is NOT the same thing as .45-70 loads for the Trapdoor Springfield vs .45-70 loads for a Ruger single shot. Not even close.

We get constantly warned about the "risk" of pressure by people who seem to believe that any deviation from a published standard is dangerous. Enough of a deviation certainly is, but all deviation is not automatically a dangerous risk.
 
M

MarkCO

New member
Good points 44AMP.

When I was testing M4 barrels to failure, we were over 200Kpsi. It took a relatively fast pistol powder to get there too.

That said, over-pressure rounds in the AR15 will wear bolts and gas rings at a faster rate, as well as gas ports.
 
M

MarkCO

New member
akinswi said:
I didnt find a difference

223 Remington has the identical 62,366 psi (430.00 MPA)

556 has Maximum pressure (EPVAT) (430.00 MPA or 62,366 psi)

So if the case dimensions are the same so are the pressures why isnt the reloading data compatible.

Also the case volume is 1% less than 223 so less case volume to me sounds like a myth more than fact
Click to expand...
Just because you don't understand it does not make it false.
 
A

akinswi

New member
MarkCO said:
Your questions and assertions paint a different picture. This is one of the reasons folks are cautious with the publication of load data.

An article published in a an online journal is not proof of anything. Your trust in your source is noted.
Click to expand...
Nope, crystal clear.

Its not rocket science we dont need a phd .
 
M

mehavey

New member
Is -- or is not -- 5.56 NATO pressure significantly different than 223Rem...

- When fired in a compatible chamber ?
- When measured in a similar manner ?

.
 
T

tangolima

New member
mehavey said:
Is -- or is not -- 5.56 NATO pressure significantly different than 223Rem...

- When fired in a compatible chamber ?
- When measured in a similar manner ?

.
Click to expand...

Same round. When fired in a .223 Remington chamber, pressure will be higher. It is because of less bullet jump (shorter free bore and possibly shorter headspace). Whether it reaches dangerous level is different thing. I don't remember reading any report that a .223 Remington rifle blew up because of that.

I don't need to worry about it as I don't have rifle with .223 Remington chamber. And I don't buy factory ammo.

-TL

Sent from my SM-N960U using Tapatalk
 
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