ObjectTemplate.SetAsynchronyFire

MDT description

This property specifies whether to fire all the firearms at the same time (= 0, default), or to fire them one by one (= 1). It is used for weapons which have multiple copies of the same weapon, i.e., AddFireArmsPosition is used multiple times for the weapon. This property is set to 1 for the B17's bombs, sub's torpedoes, and the Katyusha rocket launcher, i.e., weapons where the projectiles are fired in a series. In this way, each shot fires from a different position, cycling through the positions defined by AddFireArmsPosition.
Source and more details

Additional description

It should be noted that ObjectTemplate.addTemplate will not work for the firearm when this property is set to 1. To add an effect, use ObjectTemplate.visibleBarrelTemplate instead.