Gun SVT-40 v1.1 by asXas for Fallout 4 game.

This mod adds an SVT-40 and a SVT-40 Bayonet as standalone weapons to the Commonwealth simple as that.
(No other mods are required to run this mod)

The SVT-40 spawns on Gunners or at vendors at around level 16+.
The SVT-40 Bayonet spawns on Gunners, raiders and at vendors at level 10+ .
 (see details in the read me)
NOTE:You may need to wait/sleep 24+ hours to refresh the "loot lists".

There is also two "legendary" variants of the gun placed in the world, "Azureus" and "Krasnaya Zima" with their own custom stuff, have fun finding them!

(Note: This mod adds the gun to the leveled list trough script so it wont conflict with other mods.)

The cheating way.
If you can't be bothered to obtain the weapon normally you can follow these steps. 
Open the console and type in the following: player.additem XX000F99
(XX = the mod's # in your load order, if you're not sure what the # is you can always type "help "svt" 4 weap" in the console and look for "WEAP: svt-40"  get the weapons full ID.)