What's so good about a "set trigger"?
K
With a "normal" trigger for it to be safe you need a reasonable level of sear engagement as well as tension so that the trigger does not release under every day conditions. A lot of safeties just block the trigger lever itself and not the sear which actually holds the firing pin. But this can lead to a trigger that requires a level of force to release it and also one that a bit of movement before it releases. Careful polishing, being careful to maintain correct angles can result in lighter and smoother pull. Many of the older hammer guns from the flintlock era need quite a heavy sear to hold back a hammer - much more so than a lightweight plunger in a bolt action rifle.
A set trigger is a mechanism that provides a much lighter trigger pull, but keeping the heavy pull required to hold back the hammer. With the set trigger you have a tiny lock within the trigger mechanism that only needs a little force to hold it back. When it is released it gives a blow on the main trigger thus firing the gun.
There are many variations two most common are a double set trigger, whereby you pull the back trigger to set the front, or the push to set, where you push the trigger blade forwards to set it. Once set, the trigger just a very light touch to let it go, with minimal force or disturbance on the rifle.
I have set triggers on two rifles and occasionally use them if shooting from a well supported position, but I do find that I don't have the sensitivity to use them reliably - keep finger well off the trigger until sights are aligned and then just rest finger on the trigger and off it goes. A lot of European hunters like them for use in high seats, and have practiced and use them all the time. I had a german hunter with me a few weeks ago and he struggled with my normal trigger.
Personally I prefer a pull weight of 3 to 4 lbs that requires a firm squeeze and that goes off as tighten both hands onto the rifle - I squeeze everything in as the sights are aligned.
Most set triggers are unset when you apply the safety catch.
There is also the release trigger. I have once seen and used one on a trap shotgun. You squeeze the trigger as you say pull and it then goes off as you release your grip when you see the clay - very counter intuitive.