.223 vs .556 - Same Accuracy ?

[jrehfuss]

I have a Mossberg MVP .556 It's a bolt action with a 24" barrel 1:9 twist. Someone told me that .223 is manufactured to tighter specifactions than .556 Is that hog wash ? I will be shooting at 100 to 300 yards max targets only. Also, what weight bullets do you recommend?

Thanks, Jim

 

[ontarget]

.223/5.56 are apparently manufactured to different chamber pressure specs. This could easily effect accuracy in a particular rifle if changing back and forth. It would more likely effect your POI. As with every rifle you will need to shoot as many types of ammo as you can to see what your rifle likes best.

 

[Klint Beastwood]

I’ll go ahead and skip the “it’s the shooter that is less precise than the gun” rant and skip into what I think you are looking for.
There are throat difference in barrel specs between .223 rem, .223 wylde, and NATO.
The pressure differences is pretty common knowledge and easy to research so to skip that part, the benefit of the wylde is that it has a well researched well design spec both for pressure and for accuracy for using both NATO and .223 rem. Ultimately, the barrel will like what it likes in terms of ammo. Bullet seating, velocity, projo type etc will vary from gun to gun like and any other rifle.

 

[someguy2800]

The two chambers have different dimensions but that doesn't mean a 5.56 is automatically inaccurate. The rifle is going to be more important than the chambering. Shoot it and find out.

 

[jrehfuss]

I purchased 6 different types of .223 REM ammo. I'll experiment the next time I'm at the range. Thanks all.

 

[MEHavey]

.223/5.56 are apparently manufactured to different chamber pressure specs.

NATO is same pressure as 223REM.
The only difference is throat leade angle in the chamber to accomodate military bullet shape/seating.

 

[243winxb]

what weight bullets do you recommend?

69 gr Sierra Matchking in Black Hills Match ammo.

 

[ontarget]

NATO is same pressure as 223REM.
The only difference is throat leade angle in the chamber to accomodate military bullet shape/seating.

If that is true then why do so many shooters have a meltdown if you bring up shooting 5.56 in a .223 chamber. And why would the manufacturers warn against the same?
Not trying to start that argument up but looking for clarification.

 

[FL-NC]

I have the MVP thunder ranch model. It shoots 1 MOA or better with Black Hills 77 grain OTM (MK 262) 5.56 and also with Hornady 223 BTHP 77 grain. I had some feeding issues with the mag it came with, but it feeds well from 10 and 20 round P MAGS.

 

[MEHavey]

Because the "...throat leade angle in the chamber to accommodate military bullet shape/seating..." can -- in some instances -- lead to jam-seating/rifling pressure increases.
Which is an entirely different issue than a different cartridge pressure spec (which there isn't.)
55,000 CUP/62,000 psi

 

[denton]

The 5.56 and 223 most definitely have different pressure specifications.

Get a box of American Eagle 223, and a box of American Eagle 5.56, both of which are made at LCAAP. With the same bullet weight, the 5.56 will chronograph faster.

 

[jmr40]

Which shoots more accurately depends entirely on the individual round, the quality of the bullet used and the care with which it was loaded. Not what is on the head stamp. The cartridge cases are the same size.

There is WAY too much concern about difference between 223 and 5.56. Before the internet they were the same thing and people have been shooting them interchangeably for years. The 223 round came 1st. When the military adopted the round they re-named it 5.56. Military rifles have very slightly different specs in the chambers primarily to improve reliability. Mil-Spec 223/5.56 ammo CAN be loaded to very slightly higher pressures.

But this isn't unique to just the 223/5.56. Pick any cartridge and the rifles they are chambered in and you'll see a very wide range of pressure in the ammo and tolerances in rifle chambers. Just using 30-06 as example I can buy factory 150 gr loads that will leave the muzzle at 2700 fps, 2800, 2900, 3000, and even 3100 fps. I've run across a few factory loads, and a lot of hand loads that won't even chamber in some rifles because of the differences in the tolerances in the chambers. This causes far more real issues than the difference between 223 and 5.56.

With bolt actions I can use any of the loads ranging from 2700-3100 fps with no issues. But the problem is with semi-autos. The military Garand is designed to operate with loads around 2800 fps. Using the hotter loads won't cause the gun to blow up, but it will cause premature wear and unreliable functioning.

You run into the same issue with 223/5.56 in semi-autos. The AR platform rifles are designed to operate at slightly higher pressures than 223 chambered semi-autos. Using lower pressure 223 ammo doesn't hurt a thing in a 5.56 rifle. But if the higher pressure 5.56 ammo is used in a semi-auto designed for 223 you'll see the same issues as a Garand with higher pressure ammo.

How many 223 chambered semi-auto rifles are out there? The original Ruger Mini-14 is the only one I'm aware of and it has been rated for 5.56 for a very long time.

 

[RecoilRob]

If that is true then why do so many shooters have a meltdown if you bring up shooting 5.56 in a .223 chamber. And why would the manufacturers warn against the same?
Not trying to start that argument up but looking for clarification.

If you buy a bag of once-fired 5.56 brass and measure their lengths...you'll find all of them WAY longer than .223 max specs. The majority of this extra material is in the crimp and when you trim them to .223 length it pretty much just removes the material that had been crimped into the cannelure. If you have a tight .223 chamber this additional material will have no where to go when it tries to release the projectile and this can lead to excessively high pressures. The 5.56 chamber throats are longer to permit the crimp enough room to release properly.

 

[Offfhand]

Same rifle same accuracy. My 40-X Remington can't tell the difference and doesn't care.

 

[CoalTrain49]

I thought the pressure difference was common knowledge, but apparently it isn't. It's a wonder some people still have all of their fingers.

Saami for 5.56 NATO is 60,000 psi. 223 Remington is 55,000 psi.

Now you can argue with Hornady about that if you want, but I'm going with the published data in their 9th edition reloading manual. I'm pretty sure they load their ammo to spec.

As far as chambers, .223 Remington has a shorter throat. The reason for the longer throat in a 5.56 NATO chamber is to accommodate heavier (longer) bullets. It has nothing to do with crimp. Hornady's heaviest .223 bullet is 60 grn. Their heaviest 5.56 NATO bullet is 80 grn. Most AR barrels are 1/7 twist to accommodate the heavier bullets. 1/9 twist is common in .223 bolt guns because .223 is normally loaded with lighter bullets.

For cases, 5.56 NATO and .223 cases have the same dimensions when new. 5.56 is not longer. They are in fact the same case loaded differently. After loading .223 with range brass for awhile I've noticed that some 5.56 NATO is badly deformed at the base. Probably due to AR chambers being out-of-spec. There must be a lot of out-of-spec AR barrels out there. But then, it isn't exactly a bench rest rifle, is it.

http://www.6mmbr.com/223rem.html

 

[GunnyUSMC]

The 5.56 and 223 most definitely have different pressure specifications.

Get a box of American Eagle 223, and a box of American Eagle 5.56, both of which are made at LCAAP. With the same bullet weight, the 5.56 will chronograph faster.

This is true, most 556 is loaded at a higher pressure, but there are some that fall into the same pressure as 223.
I always hear people say that the chambers are cut different. This is almost true. What is different is the Lead, also called the Freebore, and the Throat. Everything else is the same.


For those that reload, we know that most military cases are thicker with less volume which can lead to pressure variations when loading with mixed 223 & 552 cases.

This last pic makes it very easy for those that have trouble understanding the difference between the two cartridge names.


The 223 chamber has the potential for better accuracy then the 556 due to the shorter throat and freebore .
Now if you’re shooting a bolt gun in 223, it will handle the pressure of the 556 better then a simi-auto, but you will still have the pressure.

 

[boom boom]

Luckygunner actually conducted field tests on this very issue which are posted here. Useful if you find empirical research illuminating.

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

 

[denton]

Minor points:

Most military brass is thicker than commercial brass, giving less case volume and higher pressures. That is true of all the 308 military brass that I've ever checked.

The notable exception is LC 5.56 brass. It has more case capacity than commercial brass that I've compared with, except Federal.

Because of the longer leade of 5.56, you can theoretically make cartridges that will jam into the lands of a 223 chamber. And that would cause high pressure. But those rounds would not usually fit in an AR15 magazine.

When fired in some machine guns. the bolt is so forceful and tight that it shortens the brass by an average of .014". So if you get once fired brass from a machine gun, the shoulder may be a lot farther back that you would like, raising the possibility of case head separation.

 

[GunnyUSMC]

Luckygunner actually conducted field tests on this very issue which are posted here. Useful if you find empirical research illuminating.

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

You see. I was almost right.

 

[boom boom]

Minor points:

Most military brass is thicker than commercial brass, giving less case volume and higher pressures. That is true of all the 308 military brass that I've ever checked.

The notable exception is LC 5.56 brass. It has more case capacity than commercial brass that I've compared with, except Federal.

Because of the longer leade of 5.56, you can theoretically make cartridges that will jam into the lands of a 223 chamber. And that would cause high pressure. But those rounds would not usually fit in an AR15 magazine.

When fired in some machine guns. the bolt is so forceful and tight that it shortens the brass by an average of .014". So if you get once fired brass from a machine gun, the shoulder may be a lot farther back that you would like, raising the possibility of case head separation.

That is why I prefer to buy .223 used brass rather than used LC brass if I am going to buy it. The brass fired in a SAW can be a pain to bring back to loadable condition.

 

[Powder296]

I've talked to people that have used this...

http://www.m-guns.com/tool_new.php?product=reamer

it's highly recommended by them(3 people). I will use it as well on a couple things, when I get a chance to borrow it. It's too pricey for me to buy one of my own.

 

[someguy2800]

I sectioned a couple LC 5.56 cases a few months ago just to see what the web thickness was like and I was very surprised how thin webbed they were.

 

[HankC]

I sectioned a couple LC 5.56 cases a few months ago just to see what the web thickness was like and I was very surprised how thin webbed they were.

How does LC brass web thickness compare to FC?

 

[someguy2800]

How does LC brass web thickness compare to FC?

I would have to look through my brass to find one and cut it open.

 

[hdwhit]

jrhefus asked:
Someone told me that .223 is manufactured to tighter specifactions than .556 Is that hog wash ?

No.

The "specifications" for the 223 versus the 5.56 are not "tighter". The 5.56 has a longer leade than the 223 but this is about the extent of the meaningful differences.