How can i get local axis of a projectile and apply a change of velocity to it?

I am working on a semi-realistic projectile system using line trace.
So far it work pretty well but i want to add drag using real life parameters.
I am having a lot of trouble doing that, especially applying the changes of velocity to the right axis it keep acting wrong du to it appling in world space.

How can i efficiently find the local axis of the projectile and apply a change of transform to it, from the projectile blueprint ?

thank you

I found out that I can “unrotate vector”, the previous value, apply drag to each axis as i want, and rerotate the vector back.

It seems to work really fine but is it too expensive for a small projectile ?
I am still open for better solution !

How about adding a blank parent object to the bullet blueprint and aplying the drag force to the (invisible) parent object and only rotate the bullet child?