IC is a "looser" choke - less pattern @ given distance.
I like this chart for choke selection.
It gives a good reference point for all types of shooting, keep in mind in trap @ the 16yd line, your typically shooting a clay @ approx 25 yards.
I used a mod choke in a Stoeger Long-fowler to learn with, great choice for 16, 17, 18 yards, but it's a little wide @ 19+, I've upgraded to a Verona 505LX SC now, and use a "lite full" briley choke for 16-25 yards, and 26, 27 get the full choke.
Hope that chart helps, but as always you need to pattern each choke with each type of ammo in each gun, as they are all different POA/POI.
NachO
I like this chart for choke selection.

It gives a good reference point for all types of shooting, keep in mind in trap @ the 16yd line, your typically shooting a clay @ approx 25 yards.
I used a mod choke in a Stoeger Long-fowler to learn with, great choice for 16, 17, 18 yards, but it's a little wide @ 19+, I've upgraded to a Verona 505LX SC now, and use a "lite full" briley choke for 16-25 yards, and 26, 27 get the full choke.
Hope that chart helps, but as always you need to pattern each choke with each type of ammo in each gun, as they are all different POA/POI.
NachO