Old Guns

Old Guns is a quest and achievement/trophy in Fallout 4.

Quick walkthrough
After receiving the quest, head to The Castle and talk to Ronnie Shaw. She'll guide you to the old General's room where you need to use the Workshop to clear the rubble. Inside, you'll find a turret and Sarge.

After defeating Sarge, open the door with the button on the wall and take the Artillery schematics.

Make the Artillery, assign somebody to it, and throw an Artillery Smoke Flare in the target location.

Quest stages
Return to the Castle Speak to Ronnie Shaw at the Castle Gain access to the Castle's armory Talk to Ronnie Shaw Build and assign artillery at the Castle Talk to Ronnie Shaw Follow Ronnie Shaw Head to the target area (Optional) Keep your radio on and tuned to Radio Freedom Throw a smoke flare into the target area Speak to Preston Garvey