Project Gunsmith is a mod the introduces the "Gunsmith" perk - an endgame perk in the same vein as "Jury Rigging", Gunsmith requires 75 Repair and 50 Guns. With this perk you can craft all of the firearms (small guns) mods at a workbench from various junk items, etc.

This a well thought out and well implemented modification that frees the player from waiting for unsure store restockings to get the weapon mods they want, assuming they have the skills and the sometimes rare components to make their own. To be clear, this is a balanced, enjoyable modification, and not a cheat of any kind.

A brief example of how this mod works:
-You want a scope on your hunting rifle, you can't one for sale...
-You have this mod :)
-You go to a workbench, get a list of needed items...
-You return with binoculars, surgical tubing, clamps, a whiskey bottle, scrap metal and a fork...
-You use extreme heat to melt and laboriously shape the glass, forge, cold blue and seal a scrap metal tube, install the glorious handcrafted lenses...
-You craft an adequate scope!

Later versions will add new modifications and custom work.

Enjoy my highly authentic 300 AAC Blackout alternative caliber for 5.56 weapons here: http://newvegas.nexusmods.com/mods/49290