5.56mm<.223

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Bravo11
August 25, 2003, 01:24 PM
So I'm doing a little design work here and I have a spec for a hole that calls out ø5.56mm. I say to myself no need for conversion here I know thats .223". WRONG, it's .2189. Why is this? I always see 5.56mmNATO being refered to as .223.
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Mike Irwin
August 25, 2003, 02:24 PM
.223 is the bullet diameter.

.2189 is the bore size across the lands.

.223 is the bore size across the grooves.

It's all nominal.
Bravo11
August 25, 2003, 02:35 PM
Thanks Mike,
I guess that makes sense. .004" across the peaks makes for the tight seal.
.002 per side. Probably accounts for variances in tolerance also.
gun-fucious
August 25, 2003, 02:42 PM
http://www.ammo-oracle.com/
http://www.ammo-oracle.com/images/556cham.gif
SodaPop
August 25, 2003, 05:28 PM
.223 is the bullet diameter.

I thunk it was .224?
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