Hi All...

Not only am I a new M&P 15 Sport owner, but I am new to the AR world in general and I have a rather embarrassing "newbie" question...

Other than size, what is the difference between .223 ammo and 5.56 ammo? I have learned that because my Sport is stamped 5.56 that I can use .223, and I also know that if it were reversed, that I couldn't safely use 5.56 in a .223 stamped firearm. However in real world, self defense applications, is one any better to use than the other? I have gone into some local stores and asked if they had 5.56 bulk ammo and some will show me the 5.56, but also show me .223, and some even speak of the two as if they are one in the same... I am confused! It also seems that .223 is more plentiful than 5.56..., is that typical or am I imagining that?

In regards to ammo brands, I have seen many references to Lake City as being great ammo... However, I have seen PMC is seems to be less expensive. I have also seen brands like American Eagle and TulAmmo and wonder about them... will the Sport tolerate them?

I have also seen that steel cased ammo tends to be less expensive, but have been told by some vendors to stay away from that and go with brass. Along those lines, is "Steel Match" also something to stay away from?

Bottom line, I want to make sure that I fully understand the main difference between .223 and 5.56 and also figure out which ammo (brands and case type) my Sport will best tolerate, and which I should use for range and which I should use for self defense...

I know I am asking a bunch of what may be pretty basic questions to most of you, so please know in advance that I appreciate your patience with a newbie like me!

The chambers are slightly different on a 5.56, most notably around the neck (leade) area.
Also 5.56 is generally loaded hotter than .223.
With that being said, the differences combined can cause over pressure problems, especially in older rifles.
Some ARs marked .223 can fire 5.56 as they have what is called a "Wylde" chamber, which means they were designed to fire either.

To me, 5.56 is more plentifull, especially if you take into account all the surplus/factory remanufactured ammo out there.

I stay away from Tula and other brands that are steel cased, some rifles will shoot it just fine, others will not, even Two rifles of the same brand and model may vary as to whether or not they like it.
For me, the price difference is just not worth the chance.
You bought a Ferrari and now you want to use the cheapest gas you can find?

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Hold my beer and watch this!

The .223 is rated at 52,000 cup and 5.56 NATO M193 is also rated at 52,000 cup. The SAAMI interchangeability warning came out in 1979 before the military switched to the M855 round which is rated at 55,000 cup.

Prior to 1979 with some batches of powder Lake City was allowed to load M193 ammunition to 60,000 cup to obtain the required velocities.

If M855 is fired in a .223 with a short throated chamber the .223 will develop a chamber pressure of 60,000 cup or 8,000 cup higher than its rated chamber pressure.

With any barrel marked 5.56 you will be safe to shoot any .223 or 5.56 ammunition.

I have fired new Federal M193 ammo from my .223 bolt action without any pressure signs or ill effects, "BUT" Lake City is not governed by SAAMI standards and some of their ammo might exceed SAAMI rated chamber pressures for the .223.

I have shot both steel case and brass case factory ammunition and my reloads from my AR without any malfunctions.

As a side note the European CIP the equivalent of the American SAAMI considers the .223 and 5.56 to be one in the same and have no pressure warnings or interchangeability warnings for this cartridge.

Bottom line...the difference between .223 and 5.56x45 is in the chamber. I myself have yet to see any ammo that the sport wont shoot and run well, some of it is dirtier than others and some is not as accurate but it all works really well in an AR with a 5.56 chamber

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Grover Oathkeeper

Thanks for the responses... What I am getting from this is that when viewed from the perspective of the M&P 15 Sport (chambered in 5.56) there is little difference between the two rounds, at least for all practical purposes, and it can boil down to personal preferences. Is that a correct take?

Regarding ammo brands... Gunslinger808, I didn't mean to insinuate that I want to buy the cheapest ammo out there... (although in the real world I actually do buy the cheap gas and find it gets me from point A to point B without any issue. Of course, I don't drive a Ferrari - but wish I did, LOL). However, that is precisely why I posed the question... what ammo brands warrant consideration over others? From what I see, the Sport is a Champ that will eat whatever you give it! That is a beautiful thing!

You guys are great... thanks for the replies!

The only real differences as far as your rifle is concerned is the bullet loads.
For 5.56, most are FMJ, with .223 loads you have everything from FMJs, soft points, hollow points, heavier, lighter, match, on and on.
Yup, it's all about personal preference.

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Hold my beer and watch this!

One thing to keep in mind, some 5.56 ammo is loaded with a steel core bullet. The range I belong to and a lot of others, won't let you shoot it because it is armor piercing. Would hate to see someone buy a case and not have a place to shoot it.

Good point Gomizzou.

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Hold my beer and watch this!

5.56 vs .223 – What You Know May Be Wrong

The M855 is NOT an AP round. The military designates it as a "ball" round. The ATF also does not classify it as an AP round. It was designed to be able to penetrate at longer ranges than the M193 (500-600 yrds). I do agree that there are ranges that restrict its use and that it will penetrate further than a lead jacketed round. My local indoor range does not allow "Green Tip" ammo.

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Improvise, Adapt, Overcome

Interesting article, but lots of inacurracies (or conflicting info) in it.
The 5.56 mm NATO and .223 Remington cartridges and chamberings are similar but not identical, as military 5.56 cases are often made thicker and therefore have less case capacity. (to function in MGs and SAWs).
However, the NATO specification allows a higher chamber pressure (different powders and burn rates).
NATO EPVAT test barrels made for 5.56 mm NATO also measure chamber pressure at the case mouth, as opposed to the location used by the United States civil standards organization SAAMI.
The piezoelectric sensors or transducers NATO and SAAMI use to conduct the actual pressure measurements also differ, this difference in measurement method accounts for upwards of 20.000 psi difference in pressure measurements (not much in an old Remington 700, huh?).
This also means the NATO EPVAT maximum service pressure of 62.000 psi for 5.56 mm NATO, is reduced by SAAMI to 55,000 psi for .223 Remington.
In contrast to SAAMI, the other main civil standards organization C.I.P. (European manufacture standards) defines the maximum service and proof test pressures of the .223 Remington cartridge equal to the 5.56 mm NATO.
I'd also like to see him Magna Flux the barrel on the remington 700 he used, there will probably be stress fractures noted.

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Hold my beer and watch this!

I've read mostly good reviews on PMC ammo. It is a brass cartridge and is non-corrosive. I picked up some today and will run some through my Sport hopefully in the next few days.

5.56 Nato PMC 62 gr Green Tip-LAP X-Tac 20 Rnds .
Sometimes referred to as Light Armor Penetrator. What ever you call it, it damages metal frames and falling plates, and that's why they won't let you shoot it.

I have shot lots of PMC Bronze and PMC X-Tac 5.56. They are my favorite rounds. I also bought a case (1000 rds) of Freedom Munitions remanufactured M193. I've shot a few hundred rounds but not really tested it yet.

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Improvise, Adapt, Overcome

Yeah, well, this is one of those we'll have to agree to disagree threads.
Sorta like the old 9mm vs .45 argument.
I appoligize if I seem to have posted bad info, but this is what I was going off of, from a release by the Federal cartridge folks (who make Lake City 5.56 as well as .223 LEO ammo):
http://le.atk.com/pdf/223VS556.pdf

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Hold my beer and watch this!

Gunslinger808

I have three five gallon buckets of mixed .223 and 5.56 once fired brass, the Remington .223 cases weigh the same as Lake City cases. The weight difference is a myth compaired to the weight difference between Lake City 7.62 and 30-06 cases.



Also how can you say CIP considers the chamber pressures equal for the 5.56 and .223 and yet say you would like to see him Magna Flux his Remington 700 barrel. You are contradicting yourself!!!!!

I fire M193 in my bolt action .223 because they are rated at the same chamber pressure of 52,000 cup!

*sigh*
Like I said, we'll just have to disagree, me I tend to believe the company that makes both the Lake City 5.56 AND .223 brass.

Because CIP is the EUROPEAN version of SAAMI, and they went lazy on their testing, did you not read the differences between CIP and SAAMI?
Let me post it again:
In contrast (to me) means that they disagree.

If it's a newer rifle, you're probably OK, the problems start with early 90s and back rifles that were made by folks that didn't recognize the popularity of mil surp ammo, I'll always argue that they are NOT rated at the same pressure level.

ETA: removed smart a** reply.

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Hold my beer and watch this!

How 'bout I just say you are right, and I'm wrong.
In contrast, very few European countries even allow military caliber ammo or weapon in their border.
Hence .223 is not the 5.56, no 9mm, no .45, no 7.62X51 (or 39, or 54) .
I mean it's not like I was an armorer for the DOJ/DHS for 25 years (NFTTU), or like I spent time at Ft Benning learning my job, your superior interweb knowledge is obviously much greater than mine.
Feel better now?

ETA: Dang it, I love a good argument!

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Hold my beer and watch this!

Then the 30-06 isn't the 7.62 x 63
The .308 isn't the 7.62 x 51
And the .223 isn't some silly metric 5.56 x 45 used by Europe in NATO.

interesting study done here:

5.56 vs .223 – What You Know May Be Wrong - LuckyGunner.com Labs

Look above you, its already been posted. But thanks any way.

Sent from my DROIDX using Tapatalk 2

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Improvise, Adapt, Overcome

The only thing that matters to me is whether or not can I safely shoot 5.56 and/or .223 in my 5.56 stamped AR, which I can, so I DON'T CARE how many angels can dance on the head of one opposed to the other.

What should matter to everyone is that we all should agree the slime green tipped Z-Max bullets are only for shooting zombies.



And they are cheaper in bulk.

+1 on the green tipped bullets, see I even built a rifle just for them LOL. And I definately agree they sure are cheaper in bulk!!

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Grover Oathkeeper

47, unless they're Mil Spec, then only 46 due to thicker wings.

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Hold my beer and watch this!

Hey guys, I edited some postings here. We generally do not allow links to other discussion forums. Thanks.

Several people have tested and confirmed that this is a myth.

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Improvise, Adapt, Overcome

Montavano,

I too was curious about the Russian steel cased ammo (Tul & Wolf). I sent off a quick e-mail to Smith & Wesson posing the question as to whether the M&P 15 Sport would digest this stuff without suffering ill effect. Their answer was, "yes it will digest it with just a bit more wear on the chamber than brass cartridges. The effects are negligible."

I have shot the Tul in my Sport and it is still going and more accurate than I could ask for. I usually shoot PMC 5.56 NATO ammo for target and plinking, but if I find a good deal on some Tul ( I have found it for $4.98 a box.) I'll shot that too!! Their accuracy is about the same. For hunting and self defense, I use Hornady 75 grain TAP or Zombie Max (just in case!!)

Hope that answers the steel case question.

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The Lineman-Proud Army Dad