5.56 in a .223? I did it!!

[rwj]

I thought that primary chambering difference was in free bore lengths, with the .223 being shorter. Shorter free bores can cause higher chamber pressures and is what led to the recommendation not to fire 5.56 ammo in a .223 chamber. Whether firing 5.56 in a .223 chamber will cause failure is dependent on many factors. But it’s not worth the risk to me!

 

[dfrosch]

 

[JEFFPPC]

More internet insanity. I have shot many thousands of rounds of 5.56 in .223 chambered various rifles for 50 years. Works for me.

 

[ebb]

A milestone in firearms development for sure.

 

[Thor357]

Have a look at:

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

a properly conducted test of firing 5.56 in a true SAAMI 223 chamber measuring pressure with strain gauges. Note the words 'true SAAMI 223 chamber'. As the author points out, the chances of your factory rifle being that restrictively chambered are c

Have a look at:

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

a properly conducted test of firing 5.56 in a true SAAMI 223 chamber measuring pressure with strain gauges. Note the words 'true SAAMI 223 chamber'. As the author points out, the chances of your factory rifle being that restrictively chambered are close to nil.

Yes, luckygunner is one of the websites I looked at. Another is Gavintoobe.
Because of the info these websites provided, I decided to try my experiment.
Turns out that it worked just fine.
I did, however, run across some factory 5.56 ammo that did not chamber in my rifle. As an additional
experiment, I re-seated those bullets so that they would chamber and they too worked just fine.
According to just about everybody and every book, I am risking my gun and or life doing this. I say hogwash...as long as the round chambers safely. There are exceptions of course but in my experiment I found no significant issues.

 

[Thor357]

Just an FYI for folks, I reload.
I shoot factory ammo to establish a "control".
I then develop my ammo based off the best results from factory ammo.

 

[6bra1k]

so a couple of data points
there is about a 7kpsi diff in 223 and5.56
there is a 125% safety factor built into your rifle
the pressure diff is not going to cause a failure
no company i know in the usa sells 556 ammo that exceeds 223 data for the same internet be that has been shown here.
i use to sell reman ammo for a living. i did studies before any caliber was loaded and put out for public sale.
i sold lots of 556/223 55 fmj and 62fmjbtsc. no one blew up a gun

 

[XTR]

So tell me, would a factory 556 be ok to shoot in my custom rifles chambered with an ISSF 223 reamer?

it's funny that we cut all manner of chambers with custom reamers with dimensions that vary way more than the 223/556 differences and never think twice about working up loads that are [insert value]% above published loads, but the www wigs out over the 556/223 thing.

Commercially available rifles are proof tested to about 2x the pressure of anything your going to possibly achieve in a factory load.

Just for giggles, there are more than 2 specs.....here is a sampling

 

[Thor357]

so a couple of data points
there is about a 7kpsi diff in 223 and5.56
there is a 125% safety factor built into your rifle
the pressure diff is not going to cause a failure
no company i know in the usa sells 556 ammo that exceeds 223 data for the same internet be that has been shown here.
i use to sell reman ammo for a living. i did studies before any caliber was loaded and put out for public sale.
i sold lots of 556/223 55 fmj and 62fmjbtsc. no one blew up a gun

Actually, if both are measured at the same data point using the same methodology, there is very little pressure difference if any. It is true, according to SAAMI, that rifles are manufactured and tested beyond their design specifications. Shooting factory 5.56 ammo in a rifle designated having a .223 chamber, per SAAMI specs, will (most likely) shoot factory 5.56 ammo just fine. And I agree with your last sentence.

 

[Thor357]

So tell me, would a factory 556 be ok to shoot in my custom rifles chambered with an ISSF 223 reamer?

it's funny that we cut all manner of chambers with custom reamers with dimensions that vary way more than the 223/556 differences and never think twice about working up loads that are [insert value]% above published loads, but the www wigs out over the 556/223 thing.

Commercially available rifles are proof tested to about 2x the pressure of anything your going to possibly achieve in a factory load.

Just for giggles, there are more than 2 specs.....here is a sampling

View attachment 1344213

Yeah, I've studied this chart somewhat. I don't deal with custom barrels/reamers. I just wanted to test the statement to not shoot 5.56 ammo in a rifle chambered in .223. Turns out to be a bunch of hooey...for the most part!

 

[Thor357]

I thought that primary chambering difference was in free bore lengths, with the .223 being shorter. Shorter free bores can cause higher chamber pressures and is what led to the recommendation not to fire 5.56 ammo in a .223 chamber. Whether firing 5.56 in a .223 chamber will cause failure is dependent on many factors. But it’s not worth the risk to me!

What you say is true but it's also true reloading your ammo to the jam point in any rifle will generate higher pressures. Seating your ammo to just "barely" touch to completely off the lands reduces pressure.
When shooting factory 5.56 ammo in a rifle designated as a .223, it is wise to "test" chamber that factory 5.56 ammo to see if it chambers. If it won't, then don't shoot it or you just re-seat it until it will. However, re-seating a factory 5.56 round will likely increase pressure as well so re-seat wisely! The ones I re-seated required only a couple thou. Others required too many thou to be safe, IMHO.

 

[Thor357]

This was just an experiment to verify the paradigm to not shoot 5.56 ammo in a rifle chambered in .223.
Most said you shouldn't/can't, a scant few said you can. Who should I believe? Turns out, at least in my experiment, in my rifle, that paradigm proved to be false.
I'm done with the experiment and will most likely not be shooting factory 5.56 ammo through it again.
This is because I reload all my ammo and I choose the load and bullet that works the best in this rifle.
Which by the way is 20.8-21.0 grs. of Accurate 2460 using 77gr. SMK's @ 100yards, resulting in very consistent sub-MOA groups. I'll be heading to an area far far from my home to test this rifle out to 1000 yards and beyond in the near future. Can't wait!

 

[urbanrifleman]

The only issue I ever had with nato ss109 is sometimes the primer cups are too hard for the firing pin.

 

[Thor357]

The only issue I ever had with nato ss109 is sometimes the primer cups are too hard for the firing pin.

Hmm...I haven't tried them in this rifle. My rifle has a 1:7 twist, 22" barrel and the recommendation for a gun with that twist rate is no less than 65grs. Not saying that it wouldn't work, just haven't tried it.
I have shot a boatload through my AR and they do great and it too is a 1:7 @ 16"'s.
My friends AR has a 1:9 @ 16" and it shoots 77SMK's pretty durn well and it's not supposed to!
And I shot some 55grs. through mine and it did better than expected!

 

[tommeboy]

Actually they don't, at least in this rifle. My owners manual specifically say NOT to shoot 5.56 in it.

That is the lawyers. Perfectly safe. If you are worried then you need a new hobby. Most people that reload go way over on safe limits all the time and do not realize it. If that primer is showing signs it is getting hot then you are way over already.

 

[Thor357]

That is the lawyers. Perfectly safe. If you are worried then you need a new hobby. Most people that reload go way over on safe limits all the time and do not realize it. If that primer is showing signs it is getting hot then you are way over already.

YEP!! I completely agree!!

 

[urbanrifleman]

Hmm...I haven't tried them in this rifle. My rifle has a 1:7 twist, 22" barrel and the recommendation for a gun with that twist rate is no less than 65grs. Not saying that it wouldn't work, just haven't tried it.
I have shot a boatload through my AR and they do great and it too is a 1:7 @ 16"'s.
My friends AR has a 1:9 @ 16" and it shoots 77SMK's pretty durn well and it's not supposed to!
And I shot some 55grs. through mine and it did better than expected!

They will usually shoot about 1 moa.

 

[Thor357]

They will usually shoot about 1 moa.

Well, you are doing better than both of us then. With those 62gr. Green tips the best we've been able to get is about 1.5-2.0 MOA @ 100 yards through our AR's. Not always but usually.

 

[deadidarren]

Just about everyone that loads for a 223 is in the same pressure level as a 5.56 .

 

[AWS]

You realize that Vietnam era 5.56 was loaded with a 55r bullet and modern 5.56 is loaded with a much heavier bullet. My little Rem 600 in 223 went through many cans of Vietnam era 5.56 as I could get it free from the AF armorer and later my girlfriends dad would keep me in surplus Vietnam era 5.56 from the sheriffs dept. Yes, my Rem 600 was originally chambered in 223. I think I still have a couple bandeliers of Vietnam era 5.56 in stripper clips.