4/10ths? Is that .4MIL? At 1000 yds, that is about 14". Lucky it was a clean miss. Depending on POA, 14" on an elk could have been a gut shot, or a neck shot.
So many variables, hard to say what the error actually was.
Which direction was the wind blowing? L-R or R-L?
Varying wind at 30'above LOS, up canyon, top of ridge, thermals, etc.
Was it a full value wind?
What wind speed did you calculate?
Did you allows for spin drift as well? At 1000, depending on bullet, you could easily have had .2MIL of spin drift alone. 6"+/-.
Body position/recoil management?
Exact L-R zero?
Shooting position differences between zeroing at range and field conditions?
Amount of practice at 1000?
Rifle capability?
Shooter capability?