I think the binary rifle is a 5 shot weapon that does not have much effect when you get a headshot. I do also think that it is automatic kond of like the Needle Rifle, but it has a slower rate of fire.
To me it seems so far that it takes down shields pretty quickly while having less effects on health. I think we can think of it that way because the pulse grenade is designed to emp and I could see shield destruction in the forerunner weapons.