How do I combine weapons with special characteristics?

Solution 1:

You cannot transfer your weapon's legendary effects from one gun to another but you can transfer weapon mods from one weapon to another.

While using a weapon workbench select your Suppressed Hardened 10mm Pistol and replace/craft all of the weapon mods with the default mods. This would require building a standard muzzle, standard sights, standard magazine, standard barrel, standard grip and a standard receiver onto the pistol.

The modes that were previously on the gun like the Suppressed Muzzle mod and the Automatic Hardened Receiver are not be destroyed, instead it will be stored as a physical item in your inventory.

Next, select your Instigating 10mm pistol and attach the weapon mods to the pistol. The overall effect is the same, but it's done by putting the weapon mods on the legendary gun rather than putting the legendary effect on an already-modified gun.