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223 vrs. 5.56

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Old 11-29-2010, 05:25 PM   #1
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Default 223 vrs. 5.56

could I get A brief discription of the difference beetween 223 and 5.56 --- I prety much understand it but would like A review thanks --- Tom

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Old 11-29-2010, 05:43 PM   #2
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Here we go again. 5.56 X 45 - chamber slightly different. Longer throat is the main difference. This keeps pressures manageable. Higher max pressures, but this does not mean all ammo is higher pressure. I have seen a lot of 5.56 ammo that is slightly longer than .223 brass. This can cause pressure issues in a short throat .223. Some 5.56 brass is thicker than commercial .223 brass. This can cause issues when reloading. Thicker brass means less capacity. The same powder charge in one brand case can be overpressure in another case. Loads MUST be worked up for one set of components and re-worked for any component change.

Before anyone starts flaming, I have weighed many cases and found a little difference between 5.56 and .223 cases. I have found differences at least as significant between different brands of .223 brass.

It is not as simple as "5.56 brass is thicker". I have found wide variances in weight w/in one brand of brass. This can be as problematic as changing brands.

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Old 11-29-2010, 05:45 PM   #3
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longer throat and slightly higher pressure for the 556. Thats it.
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Old 11-29-2010, 06:52 PM   #4
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Default Writers ''different presentations'' same answer

Lots has been written on this subject; lots of folk; including robocop10mm 'cpttango30' know.
I add this from AR15;
different writers bring a different presentation.

5.56 VS .223 Ammunition and Chamber Dimensions - AR15

The primary difference between .223 Remington and 5.56 x 45 mm is that .223 is loaded to lower pressures and velocities compared to 5.56 mm. .223 Remington ammunition can be safely fired in a 5.56 mm chambered gun, but the reverse can be an unsafe combination. The additional pressure created by 5.56 mm ammo will frequently cause over-pressure problems such as difficult extraction, flowing brass, or popped primers, but in extreme cases, could damage or destroy the rifle. Chambers cut to .223 Remington specifications have a shorter leade (throat) area as well as slightly shorter headspace dimensions compared to 5.56 mm "military" chamber specs, which contributes to the pressure issues.

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 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 (SAAMI .223 Rem Proof MAP is 78,500 psi so every 5.56mm round fired is a proof load, very dangerous). The 5.56 mm

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Old 11-30-2010, 03:28 AM   #5
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Default 223 vrs. 5.56

Thanks for the replies --- I knew much of what was posted (the longer lead in 5.56 chambers) being the main difference and increased pressure in 5.56 cartridge --- one thing not mentioned is bullet jump for the 223 could result in less accuracy --- and military cases are thicker brass --- one thing that I was concened with is the presure of the two different cases are mesured in different places --- bottom line I guess is 5.56 could be dangerous in A chamber cut for 223. thanks again for replies. --- Tom ---
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Old 11-30-2010, 10:55 PM   #6
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And then there's the Wylde chamber, a sort of compromise between the two. More leade than the .223 but not as much as the 5.56 NATO. Supposedly to be more accurate and able to handle the higher pressure military rounds.

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