Mule ear locks and triggers can be somewhat confusing. The type of trigger to use will depend on the type of mule ear lock you select.
If you select a lock that has what I call a "vertically acting sear", like the Storey/Pioneer Arms lock, any single trigger can work. The trigger blade and sear are both moving in a vertical plane. The trigger blade lifts the sear bar, which drops the sear nose out of a hole in the hammer. Easy enough, but all the force of the mainspring is concentrated on a very small sear nose; expect wear. A set trigger can be successfully used with a "vertically acting sear."
If you select a traditional style mule ear lock, one that has a "horizontally acting sear", you will need to use a trigger that converts the vertical rotation of the trigger blade to horizontal, rearward movement needed to disengage the sear. One solution is to pin the trigger blade above and in front of the sear so its rearward movement would act on the sear. An alternative design would be some variation of a two-lever trigger designed by Laurie Fenton. (Fento's web site is available, but I can't find it just right now.)
In the first instance, there is a tendancy for the trigger to be placed slightly to the rear in the wrist area of the stock, while Fenton's pattern can place the trigger more forward. Laying out (designing) your gun, esp. the wrist, will be very important.
Hope this helps you! Happy new year!!!
