.223 or 5.56 Nato

[Go_Vols!]

With an AR chambered for 5.56 NATO what would be better the 5.56 or the .223 ammo.

[2 clicks low]

The RULE is use only what is stamped on the barrel.

That said there is little if any difference.

2cl

[Roland]

Doesn't matter. You can shoot either in an AR with a 5.56 chamber. Personal choice, basically.

Roland

[didactic]

A .223 operates at a slightly lower pressure than the 5.56 NATO, if both are loaded up to their max specs.  And the leade (part of the chamber, more accurately the most rearward part of the barrel), just forward of the neck, before the rifling starts, is a little longer in the 5.56.  I THINK a 5.56 chanber is a little looser in one or more other dimensions, too, but my knowledge on that is a little squishier.  So it's OK to fire .223 in a 5.56 rifle, but the reverse is not always true.  Not likely to blow up a .223 by firing 5.56 ammo in it, but function problems are more likely.

Best accuracy will be with a .223 round in a .223 chamber, all other things being equal (which of course they never are).

Some rifles, like my Rock River Arms AR clone, have what's called a Wylde chamber, which is a hybrid of the two.  Neither fish nor fowl, but I like the flexibility.

What 2 C L said is sure a safe general rule.

[slim]

.223 because it's cheaper and you can shoot more. I use cheap WPA (Wolf Performance Ammo) .223 55gr. JHP all day long and it shoots plenty good for AS events.

The targets don't know the difference and the holes are just as through with .223 as they are with 5.56. Biggest difference is there will be more holes with .223 and the more you shoot (in theory!) the better you'll get. 

Software.... not hardware.

[DaveD]

As has been stated, in a 5.56 chamber you can shoot either.  The 5.56 just runs at a higher pressure.  My
data shows an 7,800 psi difference between the 223 and 5.56 loads using the same powder and bullet (TAC & 75gr HPBT)

[Sly223]

The 5.56chamber tolerates more pressure, and is very forgiving as to what it will eat. The civilian .223, a little more finicky.When in doubt I always try to get the most practical instrument for the application, and if something can function with multiple options this is the way to go.

[JoshL]

Lots of great info on the 5.56/.223 over at the Ammo Oracle:

http://ammo.ar15.com/ammo/project/hist_diff.html

[dronning]

Another option is the .223 Wylde chamber you can run .223 or 5.56.  Often refered to the "Match" chamber and as being more accurate.

[Nickle]

Folks, the only real difference between the .223, 5.56 and Wylde chambers is the throat portion of the chamber.

Don't trust what is stamped, unless it says it has a Wylde chamber.

The twist is more important than the throat. What to use all depends on the twist rate of the barrel.

So, if it's 12" twist (the real .223), use 55 grain bullets. 62's won't stabilize well and will be inaccurate.

7" through 9" twist will have a 5.56 throat.

7" twist (issue M16A2/M16A4/M4 or current Colt), use 62 grain or heavier, 55 grain will over stabilize and usually be inaccurate.

8" twist (really 7.75" and also referred to as match twist), use 62 grain or heavier, 55 grain will work, usually not as accurate as 62 and up.

9" twist (most aftermarket AR barrels, and what's on mine), use 55 to 69 grain bullets, over 69 grain will usually not stabilize as well. Have to try both 55 and 62 grain to see which is more accurate for you, and usually you will find the variation between brands and loads than the bullet weight. I know a few guys with 9" twist barrels that have great results from Federal XM193 ammo (55 grain duplication of Mil Spec M193 ball).

If you reload, and want some tips as to what bullet to use, feel free to contact me, but make sure you know which twist barrel you have.

Here's something to consider.

Original AR's were 12" twist. I haven't checked  many Colt SP1 AR's, but I can tell you every M16A1 that was issued to me during my time in the Army clearly had "5.56 NATO" stamped on the receiver, and every one of them was 12" twist. Yet they had what was technically a ".223" chamber/throat. The M16A2's, M16A4 and M4 that were issued to me also had "5.56 NATO" stamped on them, and every one had a 7" twist.

[Roland]

You can't shoot 77gr ammo (like MK. 262 mod 0) bout of 1:8, I think.

[GEmanuel]

You can't shoot 77gr ammo (like MK. 262 mod 0) bout of 1:8, I think.

My M&P 15 has a 1/8 twist and does best with 75-77 gr HPBTs. 62gr ball is good enough for AQT shooting, but I get near 1moa with handloads.

[Roland]

My mistake, just looked it up. 1/8 can't stabilize anything over 80. My bad!

Roland

[Go_Vols!]

Thank you everyone it was all very helpfull!!!

[slim]

A note on stability....

Unless you're shooting small targets at great distance - don't worry about it.

I hear folks all the time, "You should be shooting 55s out of that barrel. Those 62s are too heavy." Or, even better, "With that barrel, you should be shooting 62s or even those new 77s!" The fact is, they read it somewhere on the internet so now they think it's gospel. Most of the people telling you those things have never even shot the different bullets at different distances. But they read it on the forum!

Like many of our IITs, they're so happy to have "knowledge" they can't wait to prove to everyone how smart they are. "One more thing...."

Yes, you should find the best barrel/bullet combination for your rifle. Yes, the general rule is use the right bullet weight for the twist rate of your barrel. But, if you're still relatively new to shooting ARs and precision shooting at distance (which you have to be if you're asking which ammo is right for your rifle on a forum full of amateurs - which is EVERY internet forum!)  you should probably save the $$$ you're going to spend on those "fancy" loads and buy a bunch of 55gr. WPA instead.

Simply put - just shoot more.

[Reddot]

Amen Slim!

[ID_Hezekiah]

x2 for what Slim said, too.  Incidently, unlike other twist/bullet weight "standards" the 5.56/.223 is less well defined because the heavier bullet stabilization issue is more depedent upon the *size" of the bullet (i.e., the length of the ogive) in this particular platform versus simply weight.  I've found the "common knowledge" to be entirely reversed in a couple of my ARs, my Colt HBAR Sportster Match with 1:7 will show no neglible accuracy difference between 55 gr and 62 gr while a heavy stainless bull barrel upper in the same twist will shoot 55 gr extremely well and scatter 62 gr like a shotgun.  The basis is there, but the rifle will shoot what it likes well and what it doesn't like not so very well.  Practice and knowing your rifle is the final answer. In spite of the Colt's tolerance, I prefer a 1:8 as a good compromise twist that is easily fed the proper fodder.

[Roland]

+1. Slim, couldn't have said it better.

[Two Wolves]

I have sure learned a lot from these posts. Thank you Nickle and Slim for your inputs.

After seeing that I could put 18 out 20 on the steel at 500 yds KD with my colt 5.56 using .223 55gr, riflemans cadence, I think this 60 year old man  will just keep on keeping on. 

~ Two Wolves

[Nickle]

A reminder to all that my post on twists and weights are general guidelines. There's always going to be exceptions to those guidelines. Some exceptions I've seen, some I've heard of and some I've learned from personal experience.

Slim pretty much summed up the bottom line. Try things, see if they work. 

Buy smaller amounts of any particular ammo until you've tried it to make sure it works in your rifle. Don't be afraid to try things others say won't work, just make sure it's safe.

Once you find a load that works, THEN buy a larger amount of it. And you should tend to stick with it.

And, I'm going to be trying a few exceptions to those guidelines myself. Just to see how far I can push some of those guidelines. I load my own, and have plenty of different weight .224 bullets I can use.