My experience is that it's difficult to guess the amount of holdunder necessary at different angles and ranges. My brother and I used to go into the woods with our .177 R9s and shoot at back lit leaves or pine cones at various angles and distances. LOL.....I've had combinations of "distance and angle" where I held dead on (not low) at a target 40 yards "horizontal distance to base of tree" with my gun zero'd at 30 yard zero and the pellet hit exactly where aimed.
The issue is the loopy trajectory of those lead badminton birdies called pellets which slow down rapidly with distance (even compared to a .22 rimfire) so "Powder burner techniques" didn't work for my .177 R9 shooting 7.9 grain pellets. This is due to the fact that from a scoped gun the pellet starts out maybe 1 1/2" to 2" below the line of sight. With a 30 yard zero the pellet must rise the scope height mounting distance above the bore to fall on the aim point at 30 yards. Well.....with my .177 R9 shooting on the horizontal with my scope the "first zero" is at about 18 yards, then the apex of the pellet flight is about 1/8" above the line of sight 26ish yards, then th epellet falls on the "far zero" at 30 yards. The pellet starting below the line of sight, to above the line of sight, to on the 30 yard zero occurs only when the pellet is shot parallel to the ground subjected to maximum gravitational pull on the side of the pellet.
For example..........
Just for arguments sake, if the gun is aimed at a target "straight up" perpendicular to the force of gravity, the pellet is still starting 1 1/2" "under" the line of sight and it also crosses the line of sight at a certain distance. Since the pellet was shot perpendicular to gravity (pellet skirt down) it will continue in a straight line across the line of sight without gravity "pulling down" the pellet in the same way when shot "on the horizontal". Now add to this "for arguments sake" the fact that pellets shot at different steep shooting angles, say 45 degrees vs 60 degrees vs 75degrees, etc will have a trajectory curves dependent on gravity pulling on the side of the pellet. Obviously, if the pellet is shot EXACTLY "straight up" and unaffected by any other force (such as the orbit orf the earth, wind, pellet instability, etc) it would fall back down and hit exactly the same spot where shot.
IMHO.......the fallacy of using "powder burner techniques" with pellet guns is that powder burners are normally zero'd at long range (compared to airguns), even the .22 rimfire are often zero'd at 50 yards, the sectional density of powder burner bullets are many times higher than a pellet. they do fly considerably flatter over normal airgun distances than pellets. I haven't found that "trig functions" work very well for MY shooting at steep angles under field conditions since a pellet shot at a 60 degree angle to the ground will fly "straighter" than when it's shot parallel to the ground.
Anywhoo.......my personal solution to the "how low to aim" was addressed by going into the woods with safe down range clearance and simply shoot at back lit leaves at various distances and angles. I usually aimed at the junction of veins in a leaf and the resulting back lit hole clearly shows the poi!
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