How Long Would It Take People To Start To Kinda Rebuild Cities/Markets After A Zombie Apocalypse?

en masse they would be very nice to have, and certainly an improvement over sharpened sticks.

I would think that the barrel and stock might be useful if you wanted to manufacture a black powder firearm. Modern actions made to fire metallic cartridges are very different from a musket lock so you’d probably have to assemble the lock from scratch.