If you want to be sure that they use the bizon, then give them a bizon and nothing else. ;D
If you want them to fire only single shots, then don't give them a weapon that fires burst.
If you want them to fire only single shot silenced then try a GlockS. Or an addon weapon.
I don't know if this can be done or not, however stuff like this is not really mission editing - it's altering the game. Mission editing stuff like scripting rarely works for things like this.
What's the underlying question? What are you trying to do?