[Myrddin]

The tumbling effect was caused by the inadequate stabilization of the 1:14 rifling used in the initial M-16. The current issue uses 1:7 rifling to stabilize a typical 62 to 69 grain round. The 1:7 rifling overstabilizes a 55 gr round pushed to 3150 fps. The guilding can spin off and bullet disintegrate. A 1:9 rifling is just about optimal for .223.

[Clean_Sweep]

The tumbling effect was caused by the inadequate stabilization of the 1:14 rifling used in the initial M-16. I stand corrected. I had forgotten they made this modification. However my point that the round is not designed to tumble remains unchanged.