Sorry for the noob question. What is the difference between 5.56nato and .223?

[Leo]

All cases weighted within the same limits. Low and high within each group were about the same difference as low and high between each group 5 grains low or high from mean was across the board.

All cases held the same amount of powder, about 3 gr deviation from standard

With a ball micrometer measuring the sectioned cases, there was a difference of taper between the web and the shoulder, but no case was consistantly thicker across the board. Again, there was variance within the brands that was similar to between the brands.

If there is a difference, it is on the spec sheet and the actual cases that make production really are not different. Short of a benchrester trick of matching cases, no one will see any difference. a 93 gr case has the same volume in every brand as any other 93 gr case. I think we worry about a factor that really isnt there.

Statistical science would require the test repeated 1000's of time, but my findings convinced me no to worry
Thanks for listening

 

[Fullmag]

Don't the 5.56 use a 62 grain bullet. The 223 uses usually 55 grainer.

 

[lovemywoods]

Don't the 5.56 use a 62 grain bullet. The 223 uses usually 55 grainer.

The typical military loads for the 5.56 are in 55 and 62 grain bullets.

While the 55 grain FMJ bullet is the most common loading for the .223 round, it can be found loaded with a wide range of bullets. I've seen them from 40 grains to 85 grains. There is likely some outside that range as well. It's an amazingly versatile round!

 

[sloughfoot]

The M193, 5.56 loaded with the 55 grain FMJ bullet is loaded to Mil-Spec and is identical to the commercial 223 loadings. Mil-Spec is about 3200 fps. Of course, some commercial loadings are not that fast. That is their choice.

It is what we fired out of all of our 223 rifles in the 70's right up to now with no ill effect. Then the internet came along and advised us old timers that we had blown up all of our rifles over the years. Or at least we endangered those around us on the firing line.

Now, the M855, 5.56 loaded with the 62 grain bullet (green tip) is a totally different animal. This is the 5.56 NATO round that is indeed loaded to higher pressures to obtain about 3100 fps with the heavier bullet. This family of loads, M855, came on the scene about 1988 or so.

When talking about the 5.56, be sure to separate the 55 grain Mil-Spec load from the 5.56 62 grain NATO load.

M193 Mil-Spec versus the M855 NATO.

There is a difference.

 

[BBill]

Rock River AR's use a Wylde chamber so you can shoot either round.

 

[Leo]

Sloughfoot, You are right about people overloading the .223. I used to look at peoples primers and by that sign alone, the pressure HAD to be way over spec. Do you remember who blew up the AR at FWRR back around 2002? I heard that WIN 296 was accidently used instead of WIN 748, but I never actually talked to the guy. I am not asking you to post a name, I was just wondering what ever happened.

 

[sloughfoot]

Yeah, he has since passed on after battling brain cancer for 5 years or so.

He thought he was loading WIN 748 but it was actually WIN 296. His illness may have been part of the mistake.

Scared the pants off all of us when the AR detonated. Many parts were never found.

I think Tim may still have pictures on his website.

http://www.ktaccuracy.com/links.htm

 

[get_armbarred]

Don't most ARs shoot both?

 

[steve666]

Isn't .308 hotter than 7.62x51?

Yes. .308 = 62,000psi v 7.62x51 = 50,000psi. Also, safe chamber headspace for the .308 Winchester cartidge is between 1.6300 and 1.6340 inches. The equivalent minimum and maximum values for 7.62x51mm NATO chambers are 1.6355 and 1.6405 inches.

 

[Stschil]

Don't most ARs shoot both?

True, however there are many older ones that do not. Make sure you check check the caliber stamp. If in doubt, have it checked. I have seen even some newer barrels that were .223 only. (they were Olympic uppers, IIRC)

 

[Taylorz71]

The M193, 5.56 loaded with the 55 grain FMJ bullet is loaded to Mil-Spec and is identical to the commercial 223 loadings. Mil-Spec is about 3200 fps. Of course, some commercial loadings are not that fast. That is their choice.

It is what we fired out of all of our 223 rifles in the 70's right up to now with no ill effect. Then the internet came along and advised us old timers that we had blown up all of our rifles over the years. Or at least we endangered those around us on the firing line.

Now, the M855, 5.56 loaded with the 62 grain bullet (green tip) is a totally different animal. This is the 5.56 NATO round that is indeed loaded to higher pressures to obtain about 3100 fps with the heavier bullet. This family of loads, M855, came on the scene about 1988 or so.

When talking about the 5.56, be sure to separate the 55 grain Mil-Spec load from the 5.56 62 grain NATO load.

M193 Mil-Spec versus the M855 NATO.

There is a difference.

Love this site, always great information from the experts.

 

[msd]

You're correct about the chamber pressures being higher, but one of the most important differences is the wall thickness of the case. 5.56mm cases have thicker walls = lower internal volume = higher pressure levels when loaded with the same loads as .223.

A 5.56mm will pressure test at about 2000psi higher than a 223 loaded with comparable powder.

You're correct to a point. The difference betwen 5.56 and .223 is the thickness of the web at the case head. The thicker web on the 5.56 raises the pressure over the standard .223 pressure. Which in turn is suitable for M16's not AR15's.

The thicker webs invariably cause pressure spikes that go beyond the 2000 psi you mention.

You can shoot .223 rds thru a barrell chambered for 5.56 and vice versa. BUT here's the kicker....
you might get away with shooting 1k of 5.56 thru a barrell chambered for .223 but it's that 1001 that the pressure will spike and ...kaboom

 

[indyjohn]

This week I wrote an email to Krieger Barrels on this topic. I wrote:

Between 2002 & 2003 I purchased a H-BAR DCM barrel in the white w/ 1:7.7 twist for my ARMALITE M15-A2. Can I safely fire ammo marked 5.56mm? To date I have always used .223 ammo.

Their reply: If it has a NATO or Wylde chamber then the answer is yes. If it has a minimum SAAMI spec .223 Rem or our match chamber, then the answer is no.

I bought the Match chamber barrel.

Also, I asked this: Can I safely fire 55gr ammo? I have always fired 69gr or heavier.

Their reply: You won't get the best accuracy out of 55 grain bullets in a 1-7.7 twist, but it is certainly safe to shoot. People do this all the time.

...