Question on ammunishin

Which is bigger, 5.56 or .223?

My understanding is that they are basically the same. Most (maybe all) ARs built in the past few years are marked ".223/5.56mm" as mine is. However some earlier ones were designated .223 only or 5.56mm only. This is just from what I have been told or what I have read. Someone will have all the details.

223 is the civilian designation.They are both 5.56 mm.there is a difference maybe someone else will chime in

they are the same. . . to a point all 5.56 chambered rifles will handle both. but a match .223 chamber will not like the 5.56 round. it has a bit thicker brass and higher pressure.

Let me ask the question in a different way. If you were "breaking in" a new rifle, would you have a preference between the two?

Depends on Rifle Ar type 5.56 bolt or ruger mini14 .223 higher chamber pressure of 5.56 works better for the ar s.

(quoted from post at 15:54:08 12/19/15) Let me ask the question in a different way. If you were "breaking in" a new rifle, would you have a preference between the two?

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What caliber is stamped on the barrel?? As stated above you can't necessarily mix and match ammo.

Think in terms as .223 being two wheel drive and 5.56 being MFWD. The MFWD will do everything that the two wheel drive will do and a whole lot more with ease, and the two wheel drive can do some things that the MFWD will, but will strain to the point of being damaged on some things that the MFWD will do. A .223 in a 5.56 works nice all day long any day of the week or year, but a 5.56 in a .223 is highly unadvisable, the same as +P and not +P.

Mark

5.56 WHAT versus .223 WHAT?

I'm going take a wild stab in the dark and assume you're asking about the 5.56 (mm) NATO cartridge, versus the .223 (inch) Remington cartridge. They have the same physical dimensions, but the 5.56 NATO is loaded to higher pressure than the SAAMI specs for .223 Remington, and there are some differences in the chamber dimensions between the two. It is generally a bad idea to shoot 5.56 NATO ammo in a rifle whose markings indicate it is chambered for .223 Remington.

If you are talking about the diameter of the barrel bores or bullets for the two rifles, they are identical. They both shoot a .224 inch diameter bullet in a barrel having a .224 inch groove diameter. As do a number of other cartridges, such as .220 Swift, .22-250, and .222 Remington.

If it was my rifle, I would be shooting handloaded ammunition, which would not be the same as either mil-spec 5.56 or SAAMI-spec .223.

As for barrel break-in, this is mostly a myth unless you have a rifle with a custom barrel. The main thing is to clean the bore every few rounds as you sight it in; use whatever ammo you intend to shoot in the future.

are you asking about ammunition? projectiles fired from a gun?

Well 5.56 MM is .2188 inches. So 5.56 MM would be .0042 larger. Now for the cartridge ?? I could not tell you as I have never owned a gun in those calibers.

(quoted from post at 13:48:33 12/19/15) they are the same. . . to a point all 5.56 chambered rifles will handle both. but a match .223 chamber will not like the 5.56 round. it has a bit thicker brass and higher pressure.

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(quoted from post at 13:48:33 12/19/15) they are the same. . . to a point all 5.56 chambered rifles will handle both. but a match .223 chamber will not like the 5.56 round. it has a bit thicker brass and higher pressure.

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For all practical purposes the .223 Remington and the 5.56 NATO cartridges ARE THE SAME, the industry pressure limit for both is 52,000 CUP. Military specs for the 5.56 call for slightly thicker brass which gives the .223 a negligible edge in case capacity. For more info see the 13th Speer reloading manual. 8)

Due to the differences in the brass thickness, the chamber in the shoulder area is larger on the 5.56. A .223 Rem will chamber safely in a 5.56 NATO, as the case will expand to fill the extra space and not cause excess chamber pressure. Accuracy may be affected, but ammunition choice can overcome it.

However, the 5.56 NATO round in a .223 chamber can cause excess chamber pressure due to the slightly smaller chamber. It's not advised to use it in an arm marked only for .223 Remington.

If I were to be making a purchase, I would go for the 5.56 NATO chamber.

The basic difference between the two is maximum pressure and throating. Some people arguably use the terms throat, leade, and freebore interchangeably. I am not getting into this semantic can of worms. Someone else can if they care to.

The miltary 5.56 is loaded to a higher pressure.
The throat/ leade of a 223 Remington rifle is shorter than that of a rifle chambered in 5.56 Nato. Some commercial rifles in 223 Remington may have been reamed to the 5.56 throat length to allow use of the Nato cartridge, but they should not be used unless the rifle is checked for this modification.

There is a third option. Some of the newer rifles are being offered in a 223 Wylde chambering which has been designed to safely use both cartridges. This is probably the best option. A 223 Wylde reamer might be used to rethroat a 223 Remington but I am not sure.

You cannot use a Wylde reamer on a 5.56 Nato chamber because the throat is already longer than the Wylde throat. That would require shortening and rechambering the barrel.
The funny thing is that the standard Ar15 magazine won't allow the use of longer cartridges that come close to touching the rifling on a Nato chamber. This was at least true on the rifles I checked.

While there is a difference in 7.62 Nato and 308 Winchester case weights and dimensions, there is really no major differences in 223 Remington and 5.56 Nato case dimensions and weights.

(quoted from post at 19:23:47 12/19/15) Well 5.56 MM is .2188 inches. So 5.56 MM would be .0042 larger. Now for the cartridge ?? I could not tell you as I have never owned a gun in those calibers.

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Nominal bore diameter vs nominal groove diameter. No difference.

From what I have read, the slope of the shoulder at the nose of the cartridge is a few degrees different. I asked the local delaer about it since I am a varmint hunter and use bolt actions mostly, he said the pressures form th5.56 were higher, but most modern rifels could handle them with no problem. The one thing he warned me about was using the steel cartridges with the lacquer coating in my bolt action. He said due to the tighter fit it would build up in the chamber and require more frequent scrubbing of the chamber to prevent shells from sticking.