I forgot why I was on here to begin with!!! ... What is a single stage trigger?
Thank You, if you can help!
A single stage trigger is a trigger in which there is no, or barely any, perceivable trigger rearward travel, typically called "take up" before the sear is released. When the trigger is pulled, it releases the sear within a couple hundredth of an inch (or thousandths of an inch for match triggers) of rearward travel from its initial position. A 3 lbs single stage trigger will release the sear at 3 lbs.
A double stage trigger has a first preliminary "take up" stage. A 3 lbs double stage trigger will typically travel backward during its first stage something like 1/8 or even 1/4 of an inch under 1.5 to 2 lbs pressure until it hits the second stage where pressure must be increased to 3 lbs to actually release the sear without further travel.
Double stage (also called "two stages") triggers were typical of 20th century military rifles (e.g. the great Mauser 98, but also French MAS, English Enfield, American Springfield, etc.) because they were considered to contribute significantly to the prevention of accidental discharges under stress.
A number of very high end match rifles also had, and still have, double stage triggers, because some shooters prefer them for deliberate ultimate precision shooting.
Double stage triggers are not to be confused with poorly adjusted "lawyer proof" single stage triggers that allow some rearward travel (typically called "creep") before the sear is released but that do not feature a distinct second stage requiring a conscious additional pull of higher strength.
Single stage triggers are generally considered to be better adapted to snap shooting (either military in close quarter battle (CQB), or civilian in close range hunting). Conversely, they are generally more prone to accidental discharge because they do not require deliberately going through the first stage before being ready to fire the rifle at the second stage.