To the author:
In America at least, the proper term is "stock", as in "lock, stock and barrel".
When you write about guns, please don't make the stupid mistakes of those MSM alleged journalists.
That phrase refers to a general store's lock (on the door), stock (the inventory of goods) and barrel (as in the pickle barrel the customers sat around playing cards on.) Otherwise you're right, a gun's furniture is usually called a stock.