If it's Quarian, why does it have an N7 logo slapped on it?
the same reason MiGs or F-16s from *insert random 3rd world "air force"* don't have Red Star/USAF roundels on them. Doesn't mean that they had anything to do with making it. Those humans were still trying to design the primitive Mauser (1895CE) when our Widow was already in use.
It was never directly stated to be Quarian in design, hell it could have been a Turian import.
Awful excuse. Why would we import tech from inferior races composed of "primitives" (Harby's words not mine)?
Yes, "efficient quarian design" apparently means "shatters your arm if fired unless you're a robot, krogan or cybernetically enhanced human"
or cybernetically enhanced quarian (i.e. all of them), whenever a loyal robot servant isn't available to do the dirty work, of course. You're soft, asari, salarians, all soft.
Nevermind that science lesson courtesy of Grunt, though. We see augmented asari firing them in ME3 (Armali sniper unit). I can even put one on a volus. Space Jebus isn't that special.
You're all trying too hard to deny that which is obvious. We invented the best pistol (Arc), the "best" "shotgun" (Reegar, though I prefer Claymoar even if it's not as efficient) and the best grenade (Arc ). We also invented the Widow until the geth propaganda film is retconned from existence.
Stay salty lesser creatures.