Peacemaker stacking is when you shoot 2 or more peacemaker rounds at once. There are two methods for stacking peacemaker shots. One method allows Jak to fire 2 peacemaker shots at once and another method allows Jak to shoot up to 5 peacemaker shots at once.
Double stacking is the peacemaker stacking method that stacks up to 2 peacemaker rounds. This was the first method of peacemaker stacking to be discovered and has no application in current speedrun categories.
Multi stacking is the peacemaker stacking method that stacks up to 5 peacemaker rounds. This variant is currently used in every Jak II speedrun category, excluding Gunless, and saves over 30 seconds.
Double stacking was first discovered by Geta92 on December 12, 2017. Geta92 would later discover the multi stack method in January 2020.