The most used muzzle thread sizes for small arms in North America are:
1/2" -28 tpi (thread per inch) .5" OD,
9/16" - 32 tpi (.5625")
5/8" - 32 tpi (.625").
These^ are the most used pitches for these diameters, but a lot others can be found.
3/4" (.750") with quite a few pitch options.