Raycast in the direction of looking plus an angle offset

Hello, I'm trying to add a recoil system to my simple FPS, till now when I shot a gun I was raycasting using

     Vector3 dir = playerCamera.transform.forward;
     ray = new Ray(playerCamera.transform.position, dir);

(playerCamera being camera attached to the player), and it worked just fine, but now every time I shoot I am using a script to calculate an angle to which the gun lerps. The script then returns an angle (float value) which I want to add to the raycast direction (just so the gun shoots where it's pointing). I went through quite a few topics on that but couldn't find anything that would work, I have tried lots of things myself (like multiplying the forward vector by Quaternion.AngleAxis) and

 Vector3 dir = Quaternion.Euler(recoil,0,0) * playerCamera.transform.forward;
         ray = new Ray(playerCamera.transform.position, dir);

(which almost works), but I always have the same problem - it only works in one direction, when I look left it shoots to the left instead of up - I belive it's got to do with local / global rotation, but couldn't fihure it out myself. Thank you for any help on the topic.