I thought the Shotgun looked rather bland, and wanted a wooden stock.
The only thing I did was the stock and lever
There are 2 textures that need to be replaced for this to work.
You create this directory path in your steamapps folder:

...SteamApps\********\counter-strike source\cstrike\materials\models\weapons\v_models\

...SteamApps\********\counter-strike source\cstrike\materials\models\weapons\w_models\

Once you have done this, you are ready to add your new skins.
CS will use a file instead of it's fgd if it exists physically.
we just create that file, rename it to return to default.
since the filename it's looking for isn't present.
see how that works?

Weapons come in 2 parts:  VIEW and WORLD.
VIEW model is what you see when you are holding the weapon.
WORLD is what you see in other people's hands and the ground (in the WORLD around you)

There are 2 versions of the world model shotgun.
one is normal resolution. the other is doubled, 1024 x 1024.
You can clearly see the detail in the texture, the flashlight, smooth crisp wood grain.

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I do say it turned out better than I imagined.