I think for many shooters it would be difficult, but I can never say impossible. Since it would be unknown what the winds, or lack thereof, would be on any given day this attempt would be made, its an unknown. Same goes for any given day of any type of rifle match, and yet, many incredible groups get shot anyway.I am sure the other disiplines have very good wind readers but have shot in switchy wind enough to know it is not possible to guess the wind within 1/2 moa 100% of the time ,also the 100 shot challenge does not shoot all the shots at 600 yds, the closer shots will be lots easier. I still think 100 out of 100 may be close to impossible to acheive
There was a time many of us old timers thought a 5", 1,000yd BR group was near impossible, but as we know, that fell sometime ago and routinely since. Similar with 600yd groups in various disciplines.