What is the average wad pressure for a target load with 18.5 Grains of powder and
1 1/8 OZ of shot in a 2 3/4 in shell with winchester AA wads

I like to see the pressure indacator on my MEC press move to tell me all the air is out and there is powder.
I would say 30 lb ( 30 is the lowest number) is good if the load crimps right

i set my wad pressure at next to nothing and just let the weight of the shot set the wad on the charge. Ive played with wad pressure in my earlier years of shot shell reloading and found the way i explained is the best way in the sense of recoil, i found with more wad pressure the harder the loads will kick. also found with light and standard trap loads that if you use to much wad pressure it pushes the wad cushion down to far and it doesnt always spring back up enough to allow the shells to crimp properly. good luck

I would try some at 40lbs all the way to 55 lbs. vangunsmith

Wad pressure is NOT necessary with plastic wads......all you need to do is load the wad over the powder so there is no air gap.....a little wad pressure don't hurt but it's not at all a requirement like it was many years ago.

No more pressure than is needed to get room for a good crimp.
This can very from 0 to 50 lbs depending on components.