yes 1:11 means 1 revolution in 11". the weight of the bullet is the major factor in rate of twist. the 223 has a pretty wide range of weight so if the rate of twist is 1:9 the heavy bullets won't shoot as well as from a 1:10. i believe i got that right. front stuffers are like 1:24. there are a lot of factors that go into it BC, weight, speed, pressures, play a role in choosing a rate of twist but its easier to choose a bullet to match rate of twist than the other way round.