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First M16 Rifles in the Vietnam War

Why do writers keep getting the 5.56mm ammunition wrong! The original M16 chambered the M193 Round designated as 5.56 and the round was essentially the 223Rem. It was not the 5.56x45 NATO round which was developed by FN in the late 70's to fire the SS109 62 grain bullet with the steel penetrator. It was accepted in the early 1980's and designated as 5.56x45 NATO. That round requires a different chamber than the M193 55gn bullet. The 5/56x45 chamber has a longer freebore and shallower throat angle. The M!6A2 and later versions were the only variants issued originally chambered for the M855/SS109 round.
 
Also those originals had a slow twist barrel (1 in 12 I think though it may have been 1 in 14). As a result the 55 grain pills were note well stabilized. Later models is much faster twist to overstabile the bullets, resulting in more accuracy at long range and better penetration. There is a good section in the history of the ordinance Department that discusses these issues at length. Today’s AR’s are a lot different than Stoner’s original.
 
I didn’t get to read the article so forgive me if this is in there. After the debacle of no cleaning equipment and powder was straightened out the rifle was really liked. With the 1:12 rifling and the high velocity the bullet would yaw almost instantly. That’s what earned it the name the meat axe.
 
Condition1 said:
I didn’t get to read the article so forgive me if this is in there. After the debacle of no cleaning equipment and powder was straightened out the rifle was really liked. With the 1:12 rifling and the high velocity the bullet would yaw almost instantly. That’s what earned it the name the meat axe.
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That was the barely stabilized round which would yaw fairly dramatically when the bullet was upset-producing damage out of proportion to its caliber. Downside was accuracy and long range and inability to penetrate body armor (helmet) at 300 yards. That was “fixed” with heavier projectiles and a much faster twist. Frankly, for a pdf for civilian use the original set up would imho be a far better option (but hey that’s me).
 
BarryinIN said:
I wouldn’t mind seeing some 1:12 or even 1:14 twist 14-16” barrels hitting the market. Some new CAR barrels.
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Troy Industries made CAR barrels, but only in the GAU-17 length, and only on built uppers.

Brownells might make what you're looking for.
 
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