[HELP ME : (] Acotr get the wrong rotation when i rotate the HMD

Hi there, excuse for a few mintues .
I really get a problem in the project after research tons of data and take a long time.

I m working for a sword fight project(4.11.2) use blueprint. During the development , such this problem makes me feel so confused.
I give motion controller(R) 's transfrom to the SwordRoot(This is my weapon) .And i can easily control sword.


But when i rotate the HMD , the weapon doesn’t get the correct rotation as i want (you can see the video below).

i rotate the small degree but the weapon seems rotate the big degree.And i dont know why the wapeon doesn’t following the controller ! : (
My project upload at dropbox ,u can download it and see the details.
And i also have some weapon resource in the content folder. u guys can download and use it as u like.

Project download link:

Really thx for ur help !