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Old June 13, 2011, 05:16 PM   #1
chadstrickland
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isnt 5.56 the metric conversion of the us measurement .223

I mean seriously ..isn't it the same freaking thing...:barf:....( pulls hair out of head ):barf::barf:
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Old June 13, 2011, 05:30 PM   #2
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It sure is...

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Old June 13, 2011, 05:34 PM   #3
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actually 5.56 mm is .218 inches ...
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Old June 13, 2011, 05:51 PM   #4
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Yep. If you ever want to figure it out in the future you can use this simple conversion. I like to use this for reasons of curiosity.
This is the conversion formula for ammo

1 inch = 1.00 Caliber = 25.4mm

Caliber x 25.4 = size in mm (Example: .45 caliber x 25.4 = 11.43 so .45 caliber = 11.43mm)

Metric designation / 25.4mm = size in Caliber (Example: 9mm / 25.4 = 0.35433 so 9mm = approximately .35 cal)
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Old June 13, 2011, 05:57 PM   #5
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The biggest difference between them is on the inside.
From what I understand, the 5.56 has a smaller powder chamber inside the brass, creating higher pressures. Hence the designation. A 5.56 shot through a .223 designated gun, might cause interesting things to happen.
That's the way it was explained to me.
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Old June 13, 2011, 06:29 PM   #6
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Same external cartridge dimensions, but,
Difference in case capacity
Difference in chamber dimensions
Difference in maximum pressure

.223 is safe in a 5.56 chamber. But not the other way around

I might be missing your question though
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Old June 13, 2011, 06:33 PM   #7
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"Yep. If you ever want to figure it out in the future you can use this simple conversion. I like to use this for reasons of curiosity.
This is the conversion formula for ammo

1 inch = 1.00 Caliber = 25.4mm

Caliber x 25.4 = size in mm (Example: .45 caliber x 25.4 = 11.43 so .45 caliber = 11.43mm)

Metric designation / 25.4mm = size in Caliber (Example: 9mm / 25.4 = 0.35433 so 9mm = approximately .35 cal) "

Or you could know there are 25.4 mm in an inch and understand elementary mathematics to simplify everything.
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Old June 13, 2011, 07:56 PM   #8
jhgreasemonkey
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Quote:
Or you could know there are 25.4 mm in an inch and understand elementary mathematics to simplify everything.
Some people including me have a hard time with mathmatics so I keep the formula handy in case I forget and need it. I posted it because I thought it might be useful to the OP next time he is wondering about bullet diameter. Maby I'm taking it the wrong way but this statement sure seems condescending.
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Old June 13, 2011, 08:05 PM   #9
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Niner4Tango is correct. They're MOSTLY identical. MOSTLY.

The most major differences are in the chamber throat (.223 is a little tighter with a shorter lead before the bullet touches the rifling) and in the the pressure (5.56 is higher pressure).

.223 is usually used for precision applications like varmint rifles. 5.56 is generally used for combat/defensive rifles. There are some hybrid chambers (like the Wylde chamber) that split the difference a bit to provide a touch more theoretical accuracy than you'd get with the 5.56 chamber but retain the ability to shoot the military surplus 5.56 ammo.

As said, don't shoot 5.56 in a .223 chamber, but .223 in a 5.56 is fine.
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Old June 13, 2011, 08:45 PM   #10
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If you have access to the older American Rifleman mags, they did a series on the history of the 5.56. It started life in the early 50's as the 22 Gustafson. That case was built on the 22 Rem Mag. The history is pretty interesting for those that like reading about firearms. Here's a blurp from the article
http://hi.baidu.com/spl900114/blog/i...272f05de9.html
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Old June 13, 2011, 09:28 PM   #11
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Thanks guys for all the help...and I know that this may be a fluke but unknown to me at the time I have been shooting 5.56 in my .223 remy 78 bolt gun for 15 years with no problem...and that's a couple thousands rounds...I know it ain't alot but I never had it mess up..not saying it wont..just a luky fluke
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Old June 13, 2011, 10:02 PM   #12
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25.4 mm is exactly, not approximately one inch. The Bureau of Standards defines the inch as 25.4 mm today.

To convert caliber into gauge, divide 1.67 by the caliber and then cube the answer.

(1.67/.223)^3=420

There! It's a 420 gauge rifle.
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Old June 14, 2011, 12:33 AM   #13
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Quote:
1 inch = 1.00 Caliber = 25.4mm
Not to be pedantic, but a "caliber" is a unit of measure used to measure holes. 1 caliber = 1/100th of an inch, therefore 1" = 100 caliber. A 30-caliber rifle is not the same thing as a .30-caliber barrel.
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Old June 14, 2011, 06:08 AM   #14
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Caliber comes from the Arabian word for (bullet) mold.
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Old June 14, 2011, 06:36 AM   #15
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Quote:
As said, don't shoot 5.56 in a .223 chamber, but .223 in a 5.56 is fine.
That's not always true. The Mini-14 has a .223 chamber (with a lot of slop) and is perfectly safe to shoot both rounds.
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Old June 14, 2011, 06:39 AM   #16
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And how would a person of high caliber respond to a thread like this?

Do we need to get into the differences in bullet diameter and caliber for many cartridges? I wonder if the title was really intended to ask if 5.56x45mm was just the European designation for the .223 Remington. It was properly explained that they were close, but not the same.
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Old June 14, 2011, 08:04 AM   #17
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Quote:
Originally Posted by chadstrickland
Thanks guys for all the help...and I know that this may be a fluke but unknown to me at the time I have been shooting 5.56 in my .223 remy 78 bolt gun for 15 years with no problem...and that's a couple thousands rounds...I know it ain't alot but I never had it mess up..not saying it wont..just a luky fluke
It's more likely to be a problem with heavier weight bullets as they tend to be longer. Anytime you jam the bullet in to the leade of the barrel you have the possibility of a over pressure no matter what caliber.
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Old June 14, 2011, 01:57 PM   #18
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The Ruger Mini 14 owners manual says it's ok to use 5.56 ammo. The Target model is for .223 only

Apparently, they tightened up the chamber to improve accuracy.
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Old June 14, 2011, 07:51 PM   #19
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I know 556 is not safe in a TC contender. Spiderwebs the brass which is a sign of extreme pressure.
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