The Callisto Protocol gives players a schematic for a weapon called the Skunkworks Shotgun, aka the "Skunk Gun," but it's better to wait for a free shotgun that players get later on. The Callisto Protocol has a variety of weapons for players to use against the biophage monsters that they encounter while exploring Black Iron prison, some of which are found in the game world and some that are earned by progressing through the story. Please note that this article will have some minor SPOILERS for The Callisto Protocol, so proceed with caution.
Callisto Protocol schematics can be taken to special 3D printing stations throughout the game and used to create new weapons for protagonist Jacob Lee to use. Building these schematics costs credits, which are the primary currency in the game. Callisto Protocol credits are a rare resource, and so players will want to be careful about how they spend them. Building the Skunk Gun requires 800 credits, but since players will get a shotgun for free shortly after finding the Skunk Gun schematic, it doesn't make much sense to build it.
Instead, players should wait until they progress far enough for Dani Nakamura to give them the TK4 Riot Shotgun, aka the Riot Gun. This shotgun will more than get the job done, and being able to get it for free is a huge bonus. This way, players can save their Callisto Protocol credits for other things, like upgrading the weapons they already have, crafting ammo, etc.
That being said, the Skunk Gun in Callisto Protocol does have an impressive damage stat right off the bat, whereas the Riot Gun needs to be upgraded a bit before it gets there. The increased damage doesn't make it worth building the Skunk Gun over using credits on other things, but it's not like the Skunk Gun is useless or anything. When The Callisto Protocol adds New Game+ next year, those on their second playthroughs may want to dedicate some credits to building it so they can have Jacob's full arsenal at their disposal.
As far as Callisto Protocol upgrades go, the best bet in the game is to upgrade the Stun Baton as much as possible. The Callisto Protocol is focused on melee combat over ranged encounters, and so the Stun Baton is easily the most-used weapon in the game. Having a powerful Stun Baton is key for success, and so players should focus on it first and the guns second.
The Callisto Protocol is out now for PC, PS4, PS5, Xbox One, and Xbox Series X.