Question about the 5.56-.223

[ChCx2744]

I have noticed that on some AR variants, I see the markings ".223-5.56"

I know that you shouldn't fire 5.56 out of a .223, but a .223 fired out of a 5.56 should be okay...Why would .223 be written before 5.56? Does that mean the gun is a .223 caliber or 5.56 caliber? If it was 5.56 that could shoot .223, shouldn't it be written "5.56-.223?" And am I even right or do I have it mixed up? Is it:

.223 is okay to be fired in a 5.56
5.56 is NOT okay to be fired in a .223

Am I just crazy? BAH!

 

[sjohn26]

search is your friend...................

save the bandwidth

 

[punkndisorderly]

Theoretically, .223 shot in a rifle chambered for 5.56 will not get you optimum accuracy. Theoretically, 5.56 shot in a .223 barrel is unsafe I say theoretically because, I've never heard of anyone blowing up a .223 with 5.56 and the accuracy difference isn't enough for the majority of shooters to notice. Due to other variable, you might find your 5.56 AR shoots a particular .223 load more accuratly than another 5.56 load that it just doesn't like.

However, I've never heard of anyone running into problems shooting 5.56 in a modern rifle chambered for .223. In AR's, if you have a .223 barrel, ask the manufacturer. Many will say not to worry as their firearms will take it.

 

[BornAgainBullseye]

They are externally the same! The difference in the ammo is that the 5.56 uses thicker brass and a crimped primer to lessen the chance of a failure in the field from a split case or backed out primer. Either will send the AR 15 to a grinding halt. Regardless of whatever else you hear there is no other difference and you are safe to shoot either in you chamber. Snobs will dissagree but all of them have biased opinions with no creditable facts. Here is the truth. The 5.56 chamber is looser for battlefield conditions. The 5.56 does not operate at higher pressure. It is rated to a higher pressure than a .223 but if it operated at a higher pressure then why does both .223 and 5.56 send a 55 grain at 3200. If the 5.56 had higher pressure then it would be faster. All the 5.56 is is a beefed up .223 for field use. I have shot countless rounds of both in both chambers with no problem. My .223 chambered savage 10 will shoot LCM193 into .75 at 100 yards. And my .223 handloads will send 69 grain matchkings .5 through my cousin's DCM bushmaster both rifles have been checked by us on a regular basis for throat erosion and I have taken chamber molds of his AR after the 1000 round mark with no wear. So bring the flames and remarks and links to other write ups. They will not convince me because my proof is in the puddin

 

[JohnMc]

A version of the Wylde Chamber, or some variation thereof...

 

[trstafford]

Clears the Confusion

You know from the stamping that your rifle can safely fire both 5.56 and .223 so what is the confusion on the stamping about?

 

[rcmodel]

They are marked that way to try to prevent people calling customer service to ask the same question.

Guess it didn't work.

rc

 

[nalioth]

They are marked that way to try to prevent people calling customer service to ask the same question.

Guess it didn't work.

rc

Sure it did, they came here instead.

 

[ChCx2744]

Thanks BornAgainBullseye

And to rcmodel:

I DID call Bushmaster customer service and representative "Eddie" told me that "They are the same thing. Look it up on Wikipedia." I hung up; Do you honestly expect me to continue a conversation with such a wise gun sage like "eddie?"

 

[sargenv]

They are externally the same! The difference in the ammo is that the 5.56 uses thicker brass and a crimped primer to lessen the chance of a failure in the field from a split case or backed out primer. Either will send the AR 15 to a grinding halt. Regardless of whatever else you hear there is no other difference and you are safe to shoot either in you chamber.

Maybe in an AR or bolt gun, but in a Mini-14, Ruger advises you not to use the higher pressure 5.56 in their .223 chambers.. I didn't heed that advice and ruined a Mini-14 that way. They are not the same.. 223 rem is held to SAAMI standards and operates at lower pressure. 5.56 is held to US MIL standards and obviously operates at higher pressures. They are not the same animal.

 

[HeavenlySword]

id love to see pics of your Mini 14 chamber

 

[cudaw73]

223 vs 5.56

the diff is that 223 is not NATO spec. because all NATO countries make ammo just a little diff they come up with 5.56. the main diff is in the head space. if you plan on running wolf and other (not so cheap anymore ammo) get the 5.56 NATO 1

 

[GregGry]

If the 5.56 had higher pressure then it would be faster. All the 5.56 is is a beefed up .223 for field use

If the 5.56 has the same external dimensions, and thicker brass then the .223, then why wouldn't it have higher pressure despite the same speed? Less internal space and the same amount of gun powder = higher pressure.

 

[Mags]

If the 5.56 has the same external dimensions, and thicker brass then the .223,

If the 5.56 has thicker brass then why does a .224 bullet seat in a 5.56 case without bulges in the brass?

 

[tactikel]

Higher pressure does not necessarily mean higher velocity! 5.56 nato runs at about 60k psi, .223 at 55K per SAMMI regs. Heavy and long bullets (AP, tracer, and >63 gr bullets) needed a longer throat than the .223 varmint bullet, thick (think MG) cases to handle heavy cyclical rates of fire mean less volume for powder and higher pressures. Fire a 77 gr 5.56 at 60k psi in a .223 and you will push the action to (or past) the limit. Fire a 45 gr .223 @ 3200 fps in a 5.56, and no big deal. Just shoot what is marked on your receiver.

 

[SHvar]

According to Ruger, the Mini-14 can fire the 5.56, it is chambered to do so safely. This is in the owners manual, maybe not some of their other .223 rifles though.
The 5.56 does produce higher pressures, about 12,000 lbs per square inch higher if I remember right (less expansion when fired, faster contraction). If you sit the 2 side by side (unreloaded cartridges) you can see the 5.56 is thicker, the cartridge neck is slightly shorter, the shoulders are less anged. In fact from reloading 5.56x45 I can say that the brass is not crimped, the primers pop out easier, and dont need swagged out to make the new primer fit. Factory loaded .223 need swagged out to get the new primer to fit.

 

[Mags]

In fact from reloading 5.56x45 I can say that the brass is not crimped, the primers pop out easier, and dont need swagged out to make the new primer fit. Factory loaded .223 need swagged out to get the new primer to fit.

I can attest to the exact opposite for my reloading as 5.56 brass usaually is crimped and i have to swage the pocket. Also iff 5.56 is thicker brass with the same outside dimensions of a .223 how can a .224 bullet be seated in the case neck without bulging?