When using a bow, the game checks for the Arrows enchantment level.
If a creature is immune to normal weapons you
- CANNOT hit it with a normal bow and normal arrows
- CANNOT hit it with a magical bow and normal arrows
- CAN hit it with a normal bow and magical arrows (e.g. Arrows+1)
- CAN hit it with a magical bow and magical arrows (e.g. Arrows+1)
AFAIK you plan should work on the flesh golem. Some Golems (e.g. Clay) are however immune to piercing weapons (i.e. Arrows, Spears,...)