Check Encoreclassifieds, I believe there is a section under the Encore tab that gives screw sizes for both Encores and Contenders.
Hope that helps!
Kimbo
Just rechecked Encoreclassified and this is all I found in the Encore reference section..
Front Sight Screw on Muzzleloader and 20 gauge Slug (12 gauge is likely the same, but not verified) - 8-40