Drop the chalupa.
Dear Word Detective: I always thought that “lock, stock and barrel” meant that if you bought a store complete it came with the lock to lock the door, all of the stock in the store and the barrel (presumably filled with pickles or beans or…). Then, as I was looking for parts to fix an old flintlock rifle, I realized that in the days of flintlocks people may not have bought a complete gun, but bought the parts. So, if you bought a complete “gun” it was “lock, stock and barrel.” How did I do? — Paul Reynolds.
Not bad at all, quite well in fact. And now that you folks don’t need me anymore, I’ll be downstairs, counting the cats. Actually, come to think of it, maybe now I’ll have time to teach one of them to drive, which would be enormously handy. No long trips, of course, but surely he (I’m thinking Gus would be the best bet) could run to the Post Office for me a few times a week. As long as I keep him away from cliffs (the dreaded Toonces Syndrome), I’m sure he’ll do fine.
So, is this National Musket Month or something? This is the third question I’ve answered lately that involves muzzle-loading firearms. By the way, I like your original “bought the store” explanation of “lock, stock and barrel,” meaning “all of it, everything, the whole thing,” especially the barrel of pickles. My understanding is that such “package deals” are known today as “turnkey” offers, meaning that one need only “turn the key” in the lock to be up and running whatever one is running. For some reason, however, my mind (tricky little devil that it is) always substitutes “turncoat” for “turnkey,” raising the specter of traitorous laundromats and disloyal delicatessens lurking out there somewhere. There’s another argument for letting the cat drive.
Meanwhile, back at your question, I don’t think many people actually built their own muskets when muskets were in vogue, but “lock, stock and barrel” does indeed refer to the constituent parts of the firearm. The “lock” is the firing mechanism, the “stock” is the wooden bit you brace against your shoulder, and the “barrel” is the long tube down which the bullet travels. The “lock” of a musket is called that because the mechanism resembled early locks such as might be found on a door.
The surprising thing about “lock, stock and barrel” is not that it refers to an antique firearm, but that muskets had been in use for several centuries before the phrase first appeared. The first use of the phrase in print found so far was in a letter written by Sir Walter Scott in 1817: “Like the High-landman’s gun, she wants stock, lock, and barrel, to put her into repair.” Michael Quinion, at his excellent World Wide Words website (www.worldwidewords.org), suggests that the phrase may only have come into use when the mass-manufacture of flintlocks in factories became common, making the individual parts — the locks, stocks and barrels — more standardized and interchangeable.