Hi, Lavan,
Unfortunately, on the Type 99 there really is no way to uncock the striker except by closing the bolt and pulling the trigger. If it is any consolation, I have never seen an Arisaka firing pin break. Harley is thinking of a Springfield or a Krag, which have knurled knobs, but the Arisaka doesn't work that way. Note that your rifle is a Type 99 except for the takedown parts.
Jim
[This message has been edited by Jim Keenan (edited August 29, 2000).]