[Deadwood Pike]

Hope this is the right place for this discussion, but let me through out the question:

I am looking for my firs AR 15 and have researched the web. I came across a web site call AR15.com. I had assumed, very bad of me, that 5.56 and .223 were essentially the same in configuration and dimension. What I found was the 5.56 has a higher overall capacity in its casing, its dimensions are a few thousands longer than the .223 and creates about 18,000 psi when fired from a .223 rifle bore.

However, the SAMMI standard is not the same standard for Mil Spec and the NATO 5.56. So, psi differences, as I understand it, are like apples and oranges between SAMMI and Mil Spec standards.

ArmaLite has written a white paper in 2010 saying that you can fire a 5.56 round in a .223 bore with no appreciable psi hazard to the firearm or its operator. They have fired many 100,000 of rounds from their AR15 Upper with no signs of flattened primer or gas leaks. I know that the folks at AR15.com say you can fire a .223 round in a 5.56 chamber but not the reverse.

I was hoping that we might have an AR15 armor/expert that could shed some light on this topic.

Best Regards. Mr. Pike

 

[furlong222]

I just got my first and only AR 15....I am not an expert but from what I have read on this subject a 223 is usable in a 5.56--no problem--the 5.56 is a tad longer and may contact the lands when chambered giving a pressure spike do to the "no jump" into the barrel...I have not until now heard of the Armalite study....just going to wait for some input from those that know....we have plenty of folks here that can sort it out...thanks for the post --its an issue that needs to be dealt with

 

[Sharkey]

5.56 , .223 remington and .223 wylde can be shot from any AR 15 (.223,5.56) platform ..... They are not identical but can be used ..... I have a wylde BBL and have never shot a wylde only 5.56 and .223 remingtons

I have never seen any accuracy diff in the 5.56 or .223 remington from my AR ..... cuz it shoots better than I can

 

[4T57T]

The 5.56 chamber will swallow and fire 5.56 and .223 without a hitch. The .223 chamber will take most 5.56 rounds, and many get away with it on a routine basis to the point they are believed to be 100% interchangeable, but because the 5.56 is a "military" round you have a lot of manufacturers in multiple countries so you there is chance of getting some variations in 5.56 that might not work well in a .223 chamber. The 5.56 chamber is built to account for these potential variations, the .223 chamber is built for the .223. IMO, if you want a "shooter" with good accuracy, go 5.56 and shoot away. If you want a "tack driver", go with the .223 and stay with .223 ammo. And the accuracy thing is all debatable as someone is sure to come along and point out :biggrin:

 

[centralclb]

Long story short, buy a rifle chambered in 5.56, then you will be able to shoot both thru it without any issues.

Or 223 Wylde.

 

[Cajun]

You can shoot .223 in a 5.56 barrel but cannot shoot 5.56 in a .223 marked barrel!!!

 

[Bill M]

I don't know from personal experience how they fit in each others chambers. But what I did notice; and I noticed this with the 7.62x51/308 Winchester also, is that the load data is different. The 30-06 is a different load from the Garrand.
I once read that the Nato designated rounds are lower pressure (slower) because of the auto actions as opposed to bolt actions. The auto wasn't supposed to use the higher loads.
I just noticed the load data. I didn't explain it. Just what I researched.

 

[njcioffi]

You can shoot .223 in a 5.56 barrel but cannot shoot 5.56 in a .223 marked barrel!!!

Good rule of thumb, except the Ruger Mini 14's reciever is stamped ".223 cal" (note the distinction in the word 'cal'...not '.223 rem'...which is true, but can be misleading), but as per Ruger, will chamber and fire 5.56 safely.

 

[njcioffi]

I don't know from personal experience how they fit in each others chambers. But what I did notice; and I noticed this with the 7.62x51/308 Winchester also, is that the load data is different. The 30-06 is a different load from the Garrand.
I once read that the Nato designated rounds are lower pressure (slower) because of the auto actions as opposed to bolt actions. The auto wasn't supposed to use the higher loads.
I just noticed the load data. I didn't explain it. Just what I researched.

Yes...and a lot of people get this backwards, but that's correct....308 Win has a higher SAAMI pressure tolerance than 7.62 NATO. Some early rifles (like the Ishapore L2A2) are chambered in 7.62 NATO, and the general consensus is that you should stick to the NATO round, and not use commercial .308 in them.

 

[njcioffi]

Yes...and a lot of people get this backwards, but that's correct....308 Win has a higher SAAMI pressure tolerance than 7.62 NATO. Some early rifles (like the Ishapore L2A2) are chambered in 7.62 NATO, and the general consensus is that you should stick to the NATO round, and not use commercial .308 in them.

Few months ago, was in a LGS, where a salesman was quoting the INCORRECT info re: 7.62Nato/.308Win as a selling point to a potential customer. I tried to correct him, but wound up in a 'measuring contest' with the salesman, who refused to concede that he had it wrong (his logic being that the military MUST have a higher pressure spec because they're the military). I ultimately just told the customer to look it up before chambering a .308.

 

[Deadwood Pike]

Thanks everyone for your input:

I went with the AR 15 platform chambered in 5.56. Lower and upper made by Sig, M400 enhanced. I enjoyed shooting it, and it has the quality that I have come to know from Sig. I will add one other bit of information that I obtained from the AR15.com web site.

The Mil Specs for the AR15 platform is classified as top secret. Thus, its not possible to make comparisons between the SAMMI and Mil Standard. You can not compare the two standards side by side. I did find the total casing HO2 capacity for the Military 5.562, its "30.2grs" and is more like a magnum round for the .223. The max capacity for the .223 is "29.1gr". Thus it is possible to obtain grater pressures when using a military 5.56 in a commercial grade .223, from my perspective only, not an expert.

I had to chuckle with Njcoffi's comment. The salesman who sold me the 5.56 originally tried to sale me a .223 and said the two rounds were interchangeable. He pointed to the Sig. lower where it displayed the milt-chanbering of .223/5.56. I explained to him the lower had nothing to do with the cambering of the two rounds. I explained that only the upper determines the round to be fire. In my case the upper was a 5.56 so it would fire both rounds. Hope to fire both rounds this week end and check out the accuracy.

 

[Bill M]

Thanks everyone for your input:

The Mil Specs for the AR15 platform is classified as top secret. Thus, its not possible to make comparisons between the SAMMI and Mil Standard. You can not compare the two standards side by side. I did find the total casing HO2 capacity for the Military 5.562, its "30.2grs" and is more like a magnum round for the .223. The max capacity for the .223 is "29.1gr". Thus it is possible to obtain grater pressures when using a military 5.56 in a commercial grade .223, from my perspective only, not an expert.

The comparison is in the load data from the major manufacturers. They don't load the NATO ammo to the higher levels that our civilian ammo goes to. I'm not stating why; other than what I found on research.
Are you saying that because this 5.56 NATO cartridge holds more water, that means you can load it higher than a .223?
I guess we differ on that one.

 

[njcioffi]

Thanks everyone for your input:

I went with the AR 15 platform chambered in 5.56. Lower and upper made by Sig, M400 enhanced. I enjoyed shooting it, and it has the quality that I have come to know from Sig. I will add one other bit of information that I obtained from the AR15.com web site.

The Mil Specs for the AR15 platform is classified as top secret. Thus, its not possible to make comparisons between the SAMMI and Mil Standard. You can not compare the two standards side by side. I did find the total casing HO2 capacity for the Military 5.562, its "30.2grs" and is more like a magnum round for the .223. The max capacity for the .223 is "29.1gr". Thus it is possible to obtain grater pressures when using a military 5.56 in a commercial grade .223, from my perspective only, not an expert.

I had to chuckle with Njcoffi's comment. The salesman who sold me the 5.56 originally tried to sale me a .223 and said the two rounds were interchangeable. He pointed to the Sig. lower where it displayed the milt-chanbering of .223/5.56. I explained to him the lower had nothing to do with the cambering of the two rounds. I explained that only the upper determines the round to be fire. In my case the upper was a 5.56 so it would fire both rounds. Hope to fire both rounds this week end and check out the accuracy.

Salesmen...pshwa :shot:

 

[Deadwood Pike]

Hi Bill:

Nope, Just stating research which displayed an 18,000 psi difference between load data for a 5.56 and .223. These are theoretical values but they demonstrate the possibly of significant pressure differential when firing 5.56 ammo in a .223 chamber. Like I said, I am not an expert but the data was enough to convince me to go with the 5.56 AR 15 package rather than the .223.

 

[Time Bomb]

I don't know if it is do to pressure, but when my buddy shoots his steyr aug, 5.56 brass ejects in a forward motion and the 223 goes backward. It is so repeatable we know where to stand to keep "brass scroungers" from getting our brass.

 

[redlegagent]

5.56mm vs .223 Remington

Hornadyle.com - What is the difference between 5.56 NATO and 223 Rem ammunition?

7.62 NATO vs .308 Winchester

".308 Win vs. 7.62x51--The Straight Scoop
Before we go much further, we want to address the oft-posed question "Are the .308 Winchester and 7.62x51 NATO one and the same?" The simple answer is no. There are differences in chamber specs and maximum pressures. The SAMMI/CIP maximum pressure for the .308 Win cartridge is 62,000 psi, while the 7.62x51 max is 50,000 psi. Also, the headspace is slightly different. The .308 Win "Go Gauge" is 1.630" vs. 1.635" for the 7.62x51. The .308's "No-Go" dimension is 1.634" vs. 1.6405" for a 7.62x51 "No Go" gauge. That said, it is normally fine to shoot quality 7.62x51 NATO ammo in a gun chambered for the .308 Winchester (though not all NATO ammo is identical). Clint McKee of Fulton Armory notes: "[N]obody makes 7.62mm (NATO) ammo that isn't to the .308 'headspace' dimension spec. So 7.62mm ammo fits nicely into .308 chambers, as a rule." You CAN encounter problems going the other way, however. A commercial .308 Win round can exceed the max rated pressure for the 7.62x51. So, you should avoid putting full-power .308 Win rounds into military surplus rifles that have been designed for 50,000 psi max. For more information on this interesting topic, read the following articles: Gun Zone's 30 Caliber FAQ; Cruffler.com Technical Trivia, June 2001; and last, but not least, Steve Redgwell's .308 vs 7.62x51 Analysis, which really provides a definitive explanation. Reloaders should also note that military ammo often is made with a thicker web. Consequently the case capacity of 7.62x51 brass is usually less than that of commercial .308 brass. You may need to reduce recommended .308 Winchester loads by as much as 2 full grains, if you reload with military 7.62x51 brass, such as Lake City or IMI."

:tee:

 

[planeflyer21]

This is a good reference here:

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

Jon

 

[biku324]

I would mention that we fired many hundreds of thousands of rounds of Federal 223 68 grain BTHP Match rounds from Colt AR-15s throughout the '90s and early 2000s with no trouble at all in the NMSP. There were a few individual rifles that wouldn't feed the round (mine was one), and we just issued them WW M193 ball.

The reason I remember the specific Federal load so clearly after 20 years is because it should NEVER have been used as a police duty round. Some well-meaning purchaser thought he was buying us 'the best' ammo, and thought hgollowpoints were the best anti-personnel rounds. The real problem was that the bullets (as you all know) were MATCH hollow points; problem 2 was that the rounds were not solidly crimped into the cases - we often would clear malfunctions and find the failure to feed round with the bullet pushed into the case so deeply as to be a clear hazard. I wrote a letter asking them to stop that ammo issue immediately in 1992; as a sign of my real stroke in the organization, they were still using the same ammo with exactly the same problems ten years later.

The road to hell is surely paved with good intentions.

 

[Deadwood Pike]

Brass scroungers, that a new one on me. Most of the folks here, who shoot at the DNR range, ask if they can have the brass. If you tell them no, they leave it. Its odd that people will not ask for something that does not belong to them.