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Posted: 2/17/2011 4:00:31 AM EDT
| So what is the difference between the 223 and 556 case and load. There. Must be a headspace difference or shoulder shape that prevents the use of 556 ammo in a 223 chamber. |
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Nope. Either round will chamber in either weapon. YOU must be sure not to chamber the very hot 5.56 in a .223 chamber.
There are some minor differences but they won't prevent you from chambering these rounds. ETA Let me reiterate: DO NOT, EVER chamber a 5.56 bullet in a gun that is marked and designed for a .223. The chamber pressures of a 5.56 are MUCH higher than those of a .223, and you could damage your gun, causing (in NASA terminology) a "destructive disassembly" (i.e. an explosion). |
| The 5.56 case should have heavier walls and a thicker head to handle the higher chamber pressures of the 5.56mm NATO. The cartridges may look similar externally but the 5.56 NATO should have more velocity and chamber pressure. This is analagous to the 7.62mm NATO and the .308 cartridge internal dimensions. |
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.223 and 5.56 have effectively the same case dimensions but different chamber dimensions. The 5.56 has a longer leade, the distance between the case mouth and where the rifling starts. Bullet design takes this into account. If a .223 round is placed in a 5.56 chamber, the bullet must travel a bit before it encounters the rifling. This may affect accuracy but has no effect on chamber pressure. If a 5.56 round is placed in a .223 chamber, the bullet will be jammed into the rifling causing greatly increased chamber pressures when the round is fired.
This is why either .223 or 5.56 ammo can be fired safely in a 5.56 chamber, but only .223 ammo can be safely fired in a .223 chamber. |
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