Quote Originally Posted by EdwinLi View Post
Could be the design of the gun having less recoil.

We don't know the extent of the gun technology in Eorzea only that Eorzea Gun technology began with Blacksmithing in Limsa Lominsa and since then advanced over time.

Machinist also have access to unique ammo due to their Aether pack they carry around. Something about the Aether Pack being adjusted to manipulate Aether so it can generate the Machinist's Drones and Ammo providing them unlimited supplies. So what kind of ammo the Aether Pack creates may also factor into the low recoil.
Much like magitek, it's probably more magic than machinery.

Blacksmiths don't make complicated systems of rollers, slides, and springs that would actually reduce physical recoil. That'd require precise machinery-designed parts.