As I recall, we were able to fire the old, light 5.56 Nato bullet in the late model M16s with the fast twist. In fact I think we had to use up old stocks during annual qual. Senility is a terrible thing... I think the bullet was 55 grain FMJ before we went to the 62's.

They wouldn't let us shoot hollow points or the SX bullets, but I am confident in johnch's results.

Now, if anyone knows if a 1 in 12" twist will stabilize a 60 grain bullet, I would like to know.