Quote:
Originally Posted by JaPes
I'm new to this and don't know the exact reason but someone correct me if I'm wrong. The factoids I've found:
1.) A barrel stamped 5.56 can shoot 5.56 & .223.
2.) A barrel stamped .223 should only shoot .223.
3.) Leade = the distance the projectile has to travel before it contacts the barrel's rifling.
4.) .223 leade is shorter than 5.56.
5.) .223 & 5.56 are practically the same dimensionally. The difference is in the powder charge. Powder Charge 5.56 > Powder Charge .223.
6.) Since a .223 round is designed for a shorter lead, it will be more accurate in a .223 barrel because the projectile contacts the rifling sooner. The "tighter" chamber to leade does not not require as much powder charge in a round of .223 v.s. a 5.56.
7.) A 5.56 round is designed for a longer leade. The "looser" chamber to leade allows for the higher pressures the increased powder charge generates in a 5.56.
I'm really waiting for a more experienced member to chime in. I've read posts where some individuals swear it's ok to shoot 5.56 out of a .223 barrel. Some say it's not a good idea.
As for me, I chose my M&P 15-Sport because it has a 5.56 barrel. That way I know I can safely shoot 5.56 & .223.
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You are correct. 556 pressures exceed that of a 223 Remington in the neighborhood of 10,000 psi. As far as the leade, NATO is longer, saami is shorter.
The 556 has more oomph downrange than the more sporty 223, but I find that rifles being as quirky as they are, a particular rifle may group better with one particular bullet over another in design, weight, BC, and in the case of the 556/223 AR, chamberings in general. A weapon that fires two technically different rounds adds to the mayhem of finding that sweet spot between accuracy, power, and downrange trajectory.
I hunt deer with the 223, more bullet styles available in that offering that I find suitable. But, the 556 has a slightly flatter long range trajectory and carries more energy.
As for the hub bub about accuracy differences, try out different weights in each round and you'll see that both the 556 and 223 can be accurate. I've shot 223s in a 1/8 and 1/9 barrel with good results, same for the NATO round with good results on both end of the spectrum, no more or less for either. However, light .22s, like a 45 jhp or 50 gr varmint grenade aren't stabilized that well in a fast twist barrel due to there weight. I've tried em, not really impressive. In my bolt gun however, coyote death!