I find it odd that you have a crafting system, but you don't have the ability to take scraps and parts and have a forge and melt this stuff down and reuse it to make better weapons armor and things you may be having a hard time finding. this would make building a lot more enjoyable.
If you have tons of scrap metal throw it in the forge and make some steel bars, or steel pipes, sheets etc.
Same thing goes for woodworking and crafting axes and other tools that you may need from time to time.
i can see ammo being limited and or not reproducible. honestly the way the game plays this is not really needed, as firearms are made obsolete just by their innate implementation. they give no benefit in any scenario, you fire a gun, you are basically dead.
in any case, having a more robust crafting system giving players the ability to make the tools and silent weapons (Bows/Arrows, Fletching Stations, Woodworking Stations/Lathes, Swords, Blacksmithing Stations, Armory, Forge, Metal Working Stations etc.) and equipment to make them would go a long way to making this game more enjoyable for longer playtimes.