"Stocks are on long guns.
Handguns have grips.
That's my story, and I'm sticking to it."

I observe that throughout the latest S&W product catalog, those things on handguns are always referred to as..."Grips." And never as "Stocks." That should remove any doubts as to what they should be called.
"Ergonomic checkered target grips"
"Crimson Trace® Lasergrips® for low-light shooting"
"Ergonomic, textured grip for a confident hold"
"Scalloped E-Series™ laminate wood grips for better grip and control"
"Shock absorbing grips"
"Three interchangeable, newly enhanced, textured palmswell grip sizes to fit any hand size"
"Ergonomic grips for a more comfortable grip"
"Elegant wood grips with aggressive checkering to give a better hand-hold on the firearm"


I personally tend to refer to target stocks as "stocks", and everything else as "grips."