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Discussion Starter #1
I have a Colt AR-15 Match Target HBAR in .223 and was wondering if 5.56 x 45mm would work in it as well. Someone is looking to give me a really good deal on some!
 

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Yes the Colt has a 5.56mm chamber and will shoot either.
+1

Your barrel should be stamped (might have to look close) with 5.56 NATO on the top just in front of the front sight. You're good to go.
 

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Now I'm going to confuse the issue a bit; your Colt HBAR should, as noted, be chambered in 5.56. There are slight dimensional differences between the military 5.56 round, and commercial .223. You can swap them one way, but not always the other. Someone who's certain about it will hopefully chime in, and I will refrain from making an incorrect statement about which is which.
Edit: Oooops, 5pins got it, already.
 

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Now I'm going to confuse the issue a bit; your Colt HBAR should, as noted, be chambered in 5.56. There are slight dimensional differences between the military 5.56 round, and commercial .223. You can swap them one way, but not always the other. Someone who's certain about it will hopefully chime in, and I will refrain from making an incorrect statement about which is which.
Edit: Oooops, 5pins got it, already.
5.56 NATO and .223 Remington cartridges are dimensionally identical.

It's the chambers that are slightly different between Mil-spec and SAAMI (specifically the leade).

This:

http://www.specializedarmament.com/content/skins/flat/popup_issue_100.html

Is by far the most useful site I have ever seen regarding this issue.
 

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Discussion Starter #6
Thank you for all of your answers. I checked the barrel and it does say 5.56 NATO. It also says 1:7 (whatever that means). So, I should be okay?
 

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5.56x45mm is loaded to higher pressures than SAAMI-spec .223 Rem. You may have trouble extracing if firing the MIL-pressure ammo in a SAAMI chamber. Note that just because a barrel is stamped 5.56 doesn't mean that the chamber is actually 5.56 (e.g., DPMS).

"1:7" or "1x7" refers to the twist rate of the rifling (1 turn in 7 inches). 1:7" is a comparatively "fast" twist rate that will allow stabilization of heavier bullets like 75 or 77 grains. Some barrels marked 1:9 will stabilize these bullets; others will not. The more common 1:9 twist is generally recommended for up to 69 grain bullets. 1:8, while less common, will stabilize 75/77gr bullets.

faol:
ETA: You should be good-to-go. One caveat, however: Much of the surplus ammo available for sale today have been rejected for other than cosmetic issues. I personally steer clear of XM193, as some of it has exceeded even the NATO-spec pressures by a significant amount. Most on the errornet forums will disagree with this. Caveat emptor.
 

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Discussion Starter #8
Thanks for the great info!!! The ammo isn't surplus, so I should be okay. It's American Eagle Tracer Ammo. I'll definitely be cautious of any surplus stuff though!
 

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That ammo should work just fine for some range plinking out to 100yds give or take. With that twist rate what happens is the further out your target is the greater the chance that the faster twist may cause the bullet to become unstable and start to tumble. Your 1/7 should easily handle most anything from the low 60's up to the heavier 77 grains plus. For some serious shooting buy yourself some Black Hills in the mid to upper 70 grains and watch how you put most if not all shots into one hole, that is if you do your part. If it's Wolf or something just don't expect great groups, you won't get them.

I have a 1in9 twist on mine and when I shoot quality ammo I barely can tell the difference bwtn the 55 grain all the way up to the 77 grain at 100 yards. It's at the longer distance that the weight of the bullet and the twist of the barrel will show its self of what it can or cannot do. If you plan on using it to shoot long distance or hunt with it at unknown range, go with the heavier bullets and they shouldn't let you down.

Have fun and shoot safe those little .22's go a loooong way.
 

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If the barrel is marked 5.56 and its a 1-7 twist its most likely a 5.56 chamber. Im leary of 5.56 marked chambers in 1-9 twist rates.
 

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If the barrel is marked 5.56, then the chamber id 5.56.
 

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Bob is correct. There are some manufactures out there that dont understand the diffrence.
 

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Discussion Starter #16
Thank you all for your help! I tried some 5.56 ammo (not just tracer) and she worked just fine. I'll definitely look for some of the heavier grain bullets as well to try some long distance shooting. These ARs are fun!!! Hopefully, not as addictive as 1911s. I couldn't afford the habit!!!:biglaugh:
 

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From what I've heard, you can shoot .223 in a 5.56 NATO chamber, but can not, or should not, shoot 5.56 NATO in a standard .223 chamber.

I've heard lots of good things about the .223 Wylde chamber, it supposedly eats anything and is accurate, so that will probably factor in to my next upper.
 
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