You depict the Japanese imperial chrysanthemum and I think the ideographs for "type 99".
See at:
http://www.radix.net/~bbrown/japanese_markings.html
So you probably have a Type 99 Arisaka Japanese infantry rifle, standard issue from 1939 through 1945. Caliber is 7.7x58.
Lots of information to be found under those search terms.