My new AR (pic)


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.cheese.
July 18, 2007, 01:28 AM
http://thehighroad.org/attachment.php?attachmentid=60970&stc=1&d=1184736369

I just need to get a rear sight so I can take it to the range and figure out how/where to buy Hornady 5.56 TAP to have on hand for it. I'll eventually add a holographic sight, probably an Eotech, but for the moment iron sights are fine. I probably will end up preferring them anyways.

ETA: oh yeah, I just wanted to check. I know the general rule is that .223 is fine in a 5.56 capable rifle, but not the other way around - however, is there any reason I shouldn't use .223 for range use? In other words, is it at all better for the rifle to stick to 5.56 all the time?

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brentn
July 18, 2007, 01:36 AM
Gotta love the wiki

While the 5.56 mm and .223 cartridges are very similar, they are not identical. Military cases are made from thicker brass than commercial cases, which reduces the powder capacity (an important consideration for handloaders), and the NATO specification allows a higher chamber pressure. Test barrels made for 5.56mm NATO measure chamber pressure at a the case mouth, as opposed to the SAAMI location. This difference accounts for upwards of 20,000+ psi difference in pressure measurements. That means that advertised pressure of 58,000 psi for 5.56mm NATO, is around 78,000 psi tested in .223 Rem test barrels. The 5.56 mm chambering, known as a NATO or mil-spec chambers, have a longer leade, which is the distance between the mouth of the cartridge and the point at which the rifling engages the bullet. The .223 chambering, known as SAAMI chamber, is allowed to have a shorter leade, and is only required to be proof tested to the lower SAAMI chamber pressure. To address these issues, various proprietary chambers exist, such as the Wylde chamber (Rock River Arms)[1] or the Armalite chamber, which are designed to handle both 5.56 mm and .223 equally well.

Using commercial .223 cartridges in a 5.56-chambered rifle should work reliably, but generally will not be as accurate as when fired from a .223-chambered gun due to the excessive lead.[2] Using 5.56 mil-spec cartridges (such as the M855) in a .223-chambered rifle can lead to excessive wear and stress on the rifle and even be unsafe, and the SAAMI recommends against the practice.[3] Some commercial rifles marked as ".223 Remington" are in fact suited for 5.56 mm, such as many commercial AR-15 variants and the Ruger Mini-14, but the manufacturer should always be consulted to verify that this is acceptable before attempting it, and signs of excessive pressure (such as flattening or gas staining of the primers) should be looked for in the initial testing with 5.56 mm ammunition.[4]

.cheese.
July 18, 2007, 01:52 AM
right - I already knew that.

I suppose let me rephrase this. I know you CAN SAFELY shoot .223 from a 5.56 gun. My question is are there any long term issues though that would suggest that you're better of not.

I'm not concerned about accuracy at the range if the difference in cost between ammo justifies it. I'm just wondering if anybody has found that over long periods of time - it's better to use 5.56 in a 5.56 rifle.

RockyMtnTactical
July 18, 2007, 02:08 AM
Nope, no issues shooting .223 in a 5.56 barrel, short term or long term.

BTW, nice rifle!

taliv
July 18, 2007, 08:47 AM
hey, nice rifle

but why do you have 17 rnds next to 30 rnd mags?

Dave Markowitz
July 18, 2007, 08:53 AM
Nice rifle. No problem with shooting .223 in a 5.56 gun. My main practice load for my Colt 6721 is American Eagle .223 55 grain FMJ.

.cheese.
July 18, 2007, 04:33 PM
taliv - because I was too lazy to open another box. :neener: I had a partially used and already open box, so I just used the cartridges in it for the photo. Didn't think anybody would actually count it! lol

Frog48
July 18, 2007, 06:00 PM
I just need to get a rear sight so I can take it to the range and figure out how/where to buy Hornady 5.56 TAP

Sights:

http://www.cheaperthandirt.com/mountssi_biih.htm

TAP:
http://www.cheaperthandirt.com/defenseh_gh.htm

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