Changing Sight Height above bore - how does that affect trajectory?

[superlative]

If I want a 50 yard zero for a 7.62x39 rifle,

but I only have a 25 yard range..

and I look at a trajectory table that shows with a 1.875" sight above bore (standard AK47 iron sight), the POI at 25 yards is about .75"-0.8" low..

and I am sighting using a red dot which makes the sight about 3" above bore height...

how should I sight the rifle in?

In other words, normally if I want a 50 yard zero using an AK47 iron sight, I would sight it in at 25 yeards with the POI being about 0.8" low. However if I have a scope that makes the sight 3" above bore height, now what should the POI be? (3 minus 1.875 plus 0.8 inches = 1.925" below POA?)

Thanks!

 

[mossyhorns]

Not quite. Closer to -1.3 inches at 25 yards. Most bullet manufacturers offer free ballistic software that you can download or use to calculate everything you need.

In my experience however I always confirm zero at the actual distance.

I've had good luck with Noslers ballistic program

 

[Scout Basecamp]

A good ballistics program should allow you to input height over bore.

Applied Ballistics is top of the line, but there's lots of others out there.

The hardest part can be measuring it accurately! SKS probably isn't an issue, but some rifles bury the chamber pretty deep with lots of rails and stuff on top to get in the way. Callipers help