12,000' IS 18.8 inHp

Barometric pressure and altitude in ASL (average) are the same thing.

At 3000' (26.6 inHg) 250 yard = +2.3" @ 100 yds
At 12000' (18.8 inHg) 250 yard zero = +2.2" @ 100 yds

So, if you make no changes, assuming your rifle stays zeroed on the 10000 miles worth of flights.... the difference is about 2-3" less drop at 18.8 inHg than at 26.6" inHg.... meaning not enough to matter.


You better pray to the God of Skinny Punks that this wind doesn't pick up......