Additional Gun Mod Recipes [WIP]

Adds crafting recipes for gun mods like rifled and ported barrels, stocks, scopes, lasers, etc. WIP as all get and needs a ton of feedback on things like:

Recipe source books (current paradigm is main skill texts provide the basic fundamentals, weapon-specific books would probably include things like descriptions of parts and accessories from which you sort of mentally reverse-engineer them, hence the increased difficulty for those ones. Maybe a new book like an army field manual on equipment maintenance or an insurgent's guide to gunsmithing would be better.)
Difficulty levels (I might've highballed them compared to the difficulties for creating other similarly-complex items like revolver shotguns and finger laser CBMs)
Tools and resources required (Kevin mentioned some things like barrels and mechanisms would require a proper machine shop to fabricate, I built these based around the kind of stuff you find in gunsmith stores like welders and soldering irons, swage and die sets, hacksaws, etc so this might only work if we can get machine shop furniture and vehicle rigs set up and additional tool qualities like grinding, sanding, etc)
I see where you're coming from, but like a lot of other things plastic chunks are abstracted to heck and back: you get plastic chunks from soda bottles and the like that're flimsy as all get, but then also from things like appliances, computer consoles, arcade machines and so on which're going to be a lot more sturdy (like PC chassis side panels and the plastic sheets from microwave shells). Similar to how we can cram big-ass springs into tiny little things like hand crossbows alongside big ol' suckers like mininuke launchers and seats. Besides which, there's already precedence for plastic having enough durability to withstand some rigors as it's a major component in things like gas masks, tonfas, kukris, survivor helmets, fusion blaster rifles, et al.

I'd look at it in the sense of "you have a whole buncha' plastic scraps of all types and you just happen to have suitable pieces for the job" just as, say, you happen to have some scrap metal long and thin enough to make into a makeshift lockpick.