Any NATO marked ammo is going to be 5.56. The green tipped is 62 grain steel penetrator ammo and is called M885, and is commonly used by our military. The LC is Lake City ammo, made at a US supplier of military ammo, don't know if it is 55 grain or not.

 

 

So if I understand correctly, anything with the NATO cross the plus sign with in the circle, is considered 5.56?

 

Let me add this. YMMV. In most rifles, it doesn't matter if it is 223 or 5.56. There are some US made hunting rifles that don't shoot 5.56 as well as they do 223, but they can still shoot it safely. For any AR15 that I've had, I don't care if it is 223 or 5.56.

That NATO ammo that you have is still good ammo. It might not shoot as accurately as 223 in your rifle, but I've never heard about a dangerous event happening when someone shoots 5.56 in a rifle chambered for 223.

 

Thank you four your reply.

I did google it and found several sources that recommended against. This is one of them.

https://exclusive.multibriefs.com/c...angers-of-mixing-up-5.56x45mm-nato-and-.223-remington-rounds/recreation-leisure

 

NATO standard M193 or M855 are loaded hotter then commercial .223, and I understand that the brass is a touch thicker. A good way to tell if your rifle has a .223 chamber is if you have primer back out or popped out primers while shooting NATO standard 5.56. Lead on the rifling is too short for NATO standard.
By that same token, you can shoot .223 all day long. Not as much these days as times in the past, lots of AR15/M4 style rifles came w/ .223 chambers, as no one realized the difference until much later.
Cross in a Circle is NATO standard, although I would not be surprised if it hasn't been counterfeited.
See: https://en.wikipedia.org/wiki/List_of_military_headstamps

 

The NATO green tipped ammunition does not shoot accurately in my Colt SP-1 ones, but is fine in my Colt LE6920. Different rifling causes key holing and just poor accuracy.

 

The NATO green tipped ammunition does not shoot accurately in my Colt SP-1 ones, but is fine in my Colt LE6920. Different rifling causes key holing and just poor accuracy.

I had a Colt SP-1 new circa 1985. IIRC, the twist on it was 1:12" . I'm guessing that your LE6920 is much faster and stabilizes those heavier bullets much better. Is it 1:7" ?

We have a plain Jane Gen 1 S&W M&P Sport 15 with a 1:9" twist. It seems to shoot 55 gr well but have never tried heavier so I don't know if that is fast enough to shoot 62gr. accurately.

 

Yes. Both the AR-15 and the AR-15 Carbine are 1:12 the 6920 1:7.

 

It's an older model that I recently acquired. I have yet to. Shoot it. I am unfamiliar with what its twist is. I never thought to check.

 

Another way to distinguish 5.56 from .223 is that 5.56 cartridges are annealed (heat treated) where they are necked down as part of the NATO specs. The cases look like they were overheated at the neck and the brass will be discolored by the annealing process.

 

OP, what type of gun are you talking about? Who made it? We can give you an idea of what type of ammo it will prob prefer.

 

1:12 was designed for the 55 grain projectile. Theoretically, the faster twist rate supposedly stabilizes the heavier projectiles. Mine is a 1:8 twist. I guess it was made as a compromise but I've had very good accuracy with everything from 55 grain up to 75 grain so far. But I pretty much limit myself to Hornady for SD rounds.

 

OP, what type of gun are you talking about? Who made it? We can give you an idea of what type of ammo it will prob prefer.

Hi, I already know the caliber. Its a .223. The issue is i was given a mixed bag of ammunition . As I mentioned in the original post , the question is identifying what is 5.56 and .223. I have culled out all the headstamped .223. The remaining ammunition is not stamped with a caliber on it. Both types have the NATO cross and the # 16. One has wma and the other LC. One poster has Id'd the letters. The issue is identifying which of the remaining ammunition is 5.56. Thank you for your help.

 

I've been thinking of purchasing an AR-15 and talked to one gun shop employee about those models that shoot both .223 and 5.56. He told me the models that fire both calibers fire the .223 ammo with considerably less velocity than models chambered exclusively in .223 caliber. Is this true?

 

It's not due to the rifle other than whether it's .223, 5.56, or Wylde. 5.56 NATO is generally loaded to higher pressure than .223. That may result in slightly higher velocities. Not 'considerably less' tho. May not be any difference in velocity at all. 5.56 chambered rifles, and Wylde, will have a longer leade.
Winchester use to have an article on their website about the differences between .223 and 5.56 and which chamber a person should get and why for each.

 

Don't know any ARs that are .223 chambered. Could be. They advertise either 5.56 or Wylde. Either will do fine for .223.
Remember the Glocktalk rule. Post pictures of all new guns.

 

Any case that bears the mark of circle w/ plus sign is a military case. Winchester and Lake City respectively, 16 is the year of production.

Per military requirement, those cases will be 10% thicker and have a reduced case capacity. Adjust powder charge accordingly.

You can use the commercial. 223 cases also. They are going to be resized just the same. Load them as a separate batch.

 

Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI) says shooting 5.56mm ammunition in a firearm chambered for .223 Remington ammunition is an unsafe combination. See:

https://saami.org/wp-content/upload...-and-Ammunition-Combinations-Web-Site-and-Brochure-Master-Revised-2-18-2019.pdf

(page 8)


It's generally impossible to visually separate 5.56mm and .223 ammunition. See:

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

An excerpt:
"If you’re unfamiliar with the differences between .223 and 5.56, you should understand the following basic facts:

- The exterior (physical) dimensions of .223 and 5.56 ammunition are effectively identical.
- 5.56 ammunition may be loaded to higher pressures than .223 ammunition.
- 5.56mm chambers are dimensionally larger in certain critical areas than .223 chambers.
- Given the same ammunition, 5.56 chambers will have lower pressures than .223 chambers."

-------------------------------------------------

In my experience, you really can't separate 5.56mm/.223 "mystery ammo" (out of the original factory box) visually or by headstamp with any level of assurance, because it could be non-factory ammo (handloads) loaded into new cases with either marking.

If you have a rifle/carbine chambered for 5.56mm, and the ammo is safe (not some crappy handloads), then you should be good to shoot it. But if it shows ANY signs of being handloaded or reloaded ammo, all bets are off.

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