The RCAF stamp is definitely fake.
Wrong font, wrong dimensions, wrong broad arrow angles and size, spacing, length, etc.
You can also tell it wasn't done as one "stamp" but rather by someone using a screw driver blade, or "I" letter stamp to try and get the broad arrow done correctly, but they failed.
I have owned legitimate examples of rifles and bayonets with the "RCAF" cartouch, and seen many original examples. OP's is not one.
Also, some people above asked "why would anyone fake one", well... because it adds value. People will fake almost anything to make a dime.
My experience comes from years of collecting, handling, owning and researching this stuff.
If this rifle had a legitimate stamp under this "new" stamp, someone totally ruined it. Something is only original once.