Smooth transition from current rotation to one in animation keyframe. Is it possible?

Hi. I am searching forums for days now and i cant find answer. So i hope this is possible.

I have a player with gun. Gun rotation (aiming) is depending on position of mouse cursor when player is shooting. Than i have a idleing animation (when player is not shooting) with gun in resting position. (lowering the weapon down to his waist).

I have slow transition in animator controller from firing state to idleing but when its triggered, gun skips to default rotation (0,0,0) and then slowly goes to idleing position how it should.

But i want it to go from current rotation (last one pointing at mouse sursor) to keyframed one in animation in one smooth motion. Is it possible? Thx and sorry for my english.

For my lack of decribe skills i uploaded video HERE