Floating technology is an emerging firearm recoil reduction technique. Firearms utilizing this technology differ significantly from traditional firearm systems, featuring distinctive characteristics of a two-degree-of-freedom system. This paper presents a novel model for this floating principle machine gun, incorporating a bi-directional buffer spring. The model is established and validated against experimental results. The experiment reveals both the floating body and the automaton body exhibit quasi-harmonic motion with some randomness. An observed impact and momentum offset between the floating body and the automaton body show an offset efficiency of 29%. The stiffness of the two springs is thoroughly analyzed regarding its influence on the floating characteristics, especially the backward ending state of the bi-direction floating body, offset efficiency, and triggering consistency. Increasing the stiffness of the bi-direction floating spring raises the bi-direction floating body’s motion frequency, resulting in a delayed phase at triggering time. Likewise, augmenting the automaton spring stiffness increases its motion frequency and advances the bi-direction floating body’s phase at triggering time. These adjustments affect the relative phase between the bi-direction floating body and the automaton body, thus impacting the backward ending state, offset efficiency, and consistency.