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Discussion Starter · #1 ·
I was playing around on model1sales.com building my dream AR and it asked if i wanted it chambered in .223 or 5.56. I though that there were essentially the same so i decided to check it out. It turns out that .223 is actually 5.66 millimeters... does this .1 millimeter really make a difference in rifle? Because i shoot .223 through my AR which is chambered in 5.56... anyway just wondering if this is something that i was supposed to know and don't :confused:
 
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Discussion Starter · #3 ·
StanMac said:
I was playing around on model1sales.com building my dream AR and it asked if i wanted it chambered in .223 or 5.56. I though that there were essentially the same so i decided to check it out. It turns out that .223 is actually 5.66 millimeters... does this .1 millimeter really make a difference in rifle? Because i shoot .223 through my AR which is chambered in 5.56... anyway just wondering if this is something that i was supposed to know and don't :confused:
Its not 5.66. The .223 is 5.56 the difference is mostly dealing with the cases internal dimensions. Military brass is thicker and has less powder capacity. The barrels themselves are also slightly different in the chamber area. If you have a 5.56 chambered rifle you can shoot anything you want. If you have a .223 chambered rifle then you have to use only .223
Pat
 
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Discussion Starter · #4 ·
Alaskapopo said:
Its not 5.66. The .223 is 5.56 the difference is mostly dealing with the cases internal dimensions. Military brass is thicker and has less powder capacity. The barrels themselves are also slightly different in the chamber area. If you have a 5.56 chambered rifle you can shoot anything you want. If you have a .223 chambered rifle then you have to use only .223
Pat
Thank you very much, now i know!:cool:
 
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Discussion Starter · #6 ·
StanMac--One option to consider is Rock River's .223 Wylde chamber. It's slightly modified to still have the strength to shoot mil-spec 5.56, but will also accept .223 without sacrificing accuracy--very nice in a varmint gun or long-range shooter.

And this is my personal favorite for info about these two cartridges:

http://www.ammo-oracle.com/body.htm

Happy window shopping. :cool:
 
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Discussion Starter · #7 ·
5.56mm and .223 are not the same. You need to know the difference and what you rifle is made to handle before shooting.

.223 is the civilan designation of 5.56, but it is not the same. If you have a barrel chambered for 5.56 NATO, you can go out and buy surplus ammo and shoot it. You can also use .223 if you wish. You do not have this either/or option on a .223 chambered barrel because 5.56 primers have been known to blow back and foul the lower receiver's function.

Source: http://www.mapartsinc.com/anything.asp

I also recommend the ammo oracle (a great reference website):
http://www.ammo-oracle.com/
 
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Discussion Starter · #8 ·
yea like above a rifle chambered in 5.56 can shot 5.56 and .223 but a rifle chambered in .223 cant shoot 5.56
 
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Discussion Starter · #10 ·
  • The cartridge casings for both calibers have basically the same length and exterior dimensions.
  • The 5.56 round, loaded to Military Specification, typically has higher velocity and chamber pressure than the .223 Rem.
  • The 5.56 cartridge case may have thicker walls, and a thicker head, for extra strength. This better contains the higher chamber pressure. However, a thicker case reduces powder capacity, which is of concern to the reloader.
  • The 5.56mm and .223 Rem chambers are nearly identical. The difference is in the "Leade". Leade is defined as the portion of the barrel directly in front of the chamber where the rifling has been conically removed to allow room for the seated bullet. It is also more commonly known as the throat. Leade in a .223 Rem chamber is usually .085". In a 5.56mm chamber the leade is typically .162", or almost twice as much as in the 223 Rem chamber.
  • You can fire .223 Rem cartridges in 5.56mm chambers with this longer leade, but you will generally have a slight loss in accuracy and velocity over firing the .223 round in the chamber with the shorter leade it was designed for.
  • Problems may occur when firing the higher-pressure 5.56mm cartridge in a .223 chamber with its much shorter leade. It is generally known that shortening the leade can dramatically increase chamber pressure. In some cases, this higher pressure could result in primer pocket gas leaks, blown cartridge case heads and gun functioning issues.
  • The 5.56mm military cartridge fired in a .223 Rem chamber is considered by SAAMI (Small Arm and Ammunition Manufacturers Institute) to be an unsafe ammunition combination.
Before buying either of these two types of ammunition, always check your gun to find what caliber it is chambered for, then buy the appropriate ammunition. Most 5.56mm rounds made have full metal jacket bullets. Performance bullets - soft points, hollow points, Ballistic Silvertips, etc. - are loaded in .223 Rem cartridges. Firing a .223 Rem cartridge in a 5.56mm-chambered gun is safe and merely gives you slightly reduced velocity and accuracy. However we do not recommend, nor does SAAMI recommend, firing a 5.56mm cartridge in a gun chambered for the .223 Rem as the shorter leade can cause pressure-related problems.

http://www.winchester.com/lawenforcement/news/newsview.aspx?storyid=11
 
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Discussion Starter · #12 ·
If it makes you feel better; these days you may have harder time finding a .223 chambered AR than a 5.56 chambered AR. Most major brands of AR are pretty much offered in 5.56 chamber.
 
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Discussion Starter · #15 ·
Alaskapopo said:
The barrel should be stamped 5.56 or .223.
Pat
Yea but its usally under the hand gaurds, and so if your looking at a gun show or like you can't exactly take them off.
 
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Discussion Starter · #16 ·
Corey G said:
Yea but its usally under the hand gaurds, and so if your looking at a gun show or like you can't exactly take them off.
Actually many are stamped on the top side of the barrel, between the FSB and the flash hider. At least that's the case with my Bushy and LMT. The twist rate is also stamped.
 
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Discussion Starter · #17 ·
Here's what DPMS told me when I asked them this same question.


You will want to look at the bottom of the barrel to determine what the
chamber is cut 5.56 or .223.
All the mil-spec style barrels that we offer are cut in 5.56 and will
shot either 5.56 or .223 ammo.
If it is s bull barrel the chamber will be cut .223 and this is what we
recommend firing through it, you can use 5.56 but you may run into
feeding and extraction issues.
 
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Discussion Starter · #18 ·
If it is s bull barrel the chamber will be cut .223 and this is what we
recommend firing through it, you can use 5.56 but you may run into
feeding and extraction issues.
Thanks thats actually what I was refering too as the world of AR goes beyond the M4 style uppers.
 
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