5.56 NATO in .223 Ackley chamber

[debubba]

Would it be safe to fire 5.56 NATO in a .223 Ackley chamber.

 

[CatShooter]

Would it be safe to fire 5.56 NATO in a .223 Ackley chamber.

A 5.56 Nato what - case or loaded military round?

You can use the case - they are fine.

The loaded military round is likely to have a very long bullet, which might not stabilize if you have a slowish twist.

 

[people]

To add to that your throat might not allow safe firing of loaded ammo if that is your intention.

 

[MGYSGT]

I thought that shooting loaded 5.56/.223 is how you make Ackley brass??????????????

Tom

 

[CatShooter]

I thought that shooting loaded 5.56/.223 is how you make Ackley brass??????????????

Tom

Yes, that is how you do it.

And any NATO cartridges will shoot fine, if they chamber.

The actual exposed ogive on SS109 (green tip) is smaller than the exposed ogive of common hunting 223 ammunition.

 

[debubba]

so it won't cause excess pressure like it would fireing a5.56 in a normal .223 chamber ?

 

[CatShooter]

so it won't cause excess pressure like it would fireing a5.56 in a normal .223 chamber ?

Millions and millions of milsurp rounds of 5.56 are fired in standard 223 chambers every year - and it has been going on for more years than you can count.

In spite of myths to the contrary, there is no problem.

 

[BoilerUP]

5.56 is perfectly fine in an Ackley chamber...when fired the case will fireform to the chamber, serving to reduce pressure.

I'd bet that a LOT of people run handloads in their 223s that exceed 5.56 pressures.

 

[CatShooter]

5.56 is perfectly fine in an Ackley chamber...when fired the case will fireform to the chamber, serving to reduce pressure.

I'd bet that a LOT of people run handloads in their 223s that exceed 5.56 pressures.

You would win that bet in a New your Second!!

 

[bigedp51]

Below are the differences between a SAAMI .223 throat and a military 5.56 throat, if you fire military M855 type ammunition in a .223 with a shorter throat you will have higher chamber pressures.

The SAAMI .223/5.56 interchangeability warning came out in 1979 with the adoption of the M855 round and longer military throat.

If you fire 5.56 M855 ammunition in a .223 with the short SAAMI throat the chamber pressure will be approximately 8,000 psi higher than normal.

Now to add even more confusion, my Savage .223 with a 1 in 9 twist has a longer throat than my two AR15 rifles do. You need to figure out what your rifles twist rate is, the majority with a 1 in 14 and 1 in 12 twist will have the short throat and cause higher chamber pressures. Newer .223 rifles with 1 in 9, 1 in 8, 1 in 7 twist rates will have longer throats just like the AR15 rifles.

And CatShooter I would like to hit you on the head with a ball peen hammer and leave an impression on your mind. Look at the pressure differences in the chart above and be aware that these pressure readings are correct between a short throated .223 and a long throated 5.56. Read the link below and "HOW" the pressures were measured and the fact the pressures "WERE" higher with M855 ammunition in a short throated .223 rifle.

5.56 vs .223 – What You Know May Be Wrong
http://www.luckygunner.com/labs/5-56-vs-223/

See the throat types below for the .223, my Savage is the top listed at .0566 of freebore, the Wylde is .0619 and a standard M16/AR15 is .0500

http://www.radomski.us/njhp/cart_tech.htm

As you can see below the throat on a AR15 is twice as long and slightly larger in diameter than the SAAMI .223 throat.

 

[CatShooter]

Except, Ed... regardless of how the pressures are measured, or what throats are used - eleventy kajillion rounds of 5.56mm, 62gr ammo are fired in 223 chambers and...

... nothing bad happens.

Go to any 800 number website like Midsouth, or Natchez, and they are selling 5.56 SS109 ammo, and 90%+ of it will be shot in 223 chambers.

It is all moot in the end, cuz nothing happens. Kind of like putting O*L on your cases

And ball peen hammers are not allowed.


(I love your pictures though - keep them coming )

 

[people]

Most of the time you will be fine. Not always. The mill allows individual rounds to go as high as 70,000psi. I have a friend who liked to shoot M855 in his bolt. He blew half the primers.

Turns out his chamber is truly a .223. I am sure rem is cutting their chambers to allow 556 ammo to be fired in it.

 

[bigedp51]

Below is the milspec pressure requirements for commercial contract military M193 ammunition dated 1976. In plain English the commercial .223 pressures are the same as military 5.56 ammunition. BUT the throat was lengthened on military rifles firing M855 ammunition for the new bullet and barrel twist. This means firing M855 military ammunition in a SAAMI short throated .223 chamber raises the chamber pressure from the rated 55,000 psi to approximately 59,000 psi or 4,000 psi over the maximum rated pressure.

MIL-C-9963F
15 October 1976

MILITARY SPECIFICATION
CARTRIDGE, 5.56MM, BALL, M193

3.7 Chamber pressure.

3.7.1 Measurement by copper-crush cylinder.-The average chamber pressure of the sample cartridges, conditioned at 70° ± 2°F, shall not exceed 52,000 pounds per square inch (PSI). The average chamber pressure plus three standard deviations of chamber pressure shall not exceed 58,000 PSI.

3.7.2 Measurement by piezoelectric transducer.-The average chamber
pressure of the sample cartridges, conditioned at 70° ± 2°F, shall not
exceed 55,000 PSI. The average chamber pressure plus three standard
deviations of chamber pressure shall not exceed 61,000 PSI.


What this means above is 52,000 cup, 55,000 psi and 62,000 psi NATO EPVAT or European CIP pressure standards are all the same exact chamber pressure measured three different ways.

In plain English the firearms manufactures are making many of the newer .223 rifles with longer throats. BUT there are still .223 rifles with 1 in 12 twists and short throats floating around that will cause pressure problems. Again my factory Savage .223 rifle with a 1 in 9 twist has a longer throat than my AR15 rifles do.

Remington is selling .223 rifles with 1 in 12 twist and 1 in 9 twist and no doubt have two different throat lengths.

Again look at the green and blue pressure graphs below, if you fire a commercial .223 cartridge in a AR15 chamber the pressure is 4,000 psi "LOWER" than normal. If you fire military M855 ammunition in a .223 chamber it is 4,000 psi "HIGHER" than normal.

And Catshooter, the majority of 5.56 military type ammunition fired in civilian commercial .223 rifles is M193 ammo and the same chamber pressure as commercial .223 ammunition.

Below is a pressure and velocity chart from Quickload, and my reloads below are only loaded to 50,000 psi and my brass and barrels love me for it.