Blake Wrote:I was just reading that section last night. If memory serves, it doesn't specifically say how he recognizes that it's a 5.56 NATO. Perhaps it was implied and I missed it. (I know squat about ammo.)
I don't remember the exact words either, but the 223 Remington and the 5.56 NATO are the same round. The impression I got was that Jack looked at the headstamp . . . but it was just an impression. And I seem to remember that his thoughts were that it
wasn't the 223, but the 5.56 NATO instead. The only difference between the commercial round and the military round is a crimp around the primer pocket, and often, a flash suppressant in the powder. Other than that, they're identical.
And that circle with the plus-sign inside designates a NATO loading which is not limited to rifle ammo. I've seen it on 9mm and 308 brass as well.
What it actually means is that the round falls within NATO specs for muzzle velocity and bullet weight/ballistic coefficient, which means that it will have the same trajectory as a NATO round.
You can load the round with different bullet weights and different powders, and get a much different trajectory. Sierra Bullet Company alone offers twenty three different bullets for that cartridge, ranging in weight from 40 to 80 grains -- full metal jacket, (hard ball) soft nose for hunting varmints, all the way up to VLD (Very Low Drag) long range target bullets.
The American military used to use a 55-grain FMJ fired from a barrel with a 1-in-12 inch twist. These days, they use a 68-grain bullet fired from a barrel with a 1-in-9 inch twist.
The long range VLD target bullets weigh 80 grains and are fired from a barrel with a 1-in-7 inch twist.
Ken V.