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Originally posted by jhe888:

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Originally posted by ArtieS:
Please note that if you go with a .223 from an AR with a 1/7 twist rate, and shoot very light bullets, you may have accuracy or bullet disintegration problems.

I have no experience with this, but I have read that 1/7 can cause light bullets to fly apart from the rotational forces at high velocity. The AR platform often uses a 1/7 twist to stabilize heavy for caliber bullets that are long. An older .223 bolt gun will often have as much as a 1/12 twist barrel, while newer offerings will likely be 1/8 (Ruger American) or 1/9 (Savage Axis).

To be all ballistics nerd on you - it isn't the weight of the bullet that causes them to be less stable at 1 in 7 rate of rotation, but the length of the bullet. Faster rotation is needed to stabilize long bullets. Usually, spinning short (light) bullets too fast causes less or no problems. Since weight is a proxy for length, some think it is the weight that matters.

Being spun fast enough to self-destruct in flight is about bullet construction. Very lightly constructed bullets, like the super-light varmint bullets, may not withstand higher twist rates. If they hold up under those rotation rates, they should still be accurate, though.