I tested it in 31-08, to get arsenal dwarfs to assign bolts and hunters to equip bolts:
Have a hunter with the skill enabled. Arsenal dwarf will not assign bolts to a group without a hunter with the skill turned on.
Create a bolt group or two in military ammo screen for hunters - m - f. NEVER delete the bolt groups. If you delete it, the bolts get "locked up" and will never be reassigned. The arsenal dwarf will refill bolt groups as new bolts are made.
Turn on forbid used ammo or else your bolt groups will get filled with recycled single bolts, and your hunters will go out hunting with 2 bolts.
Hunters seem to ignore the bolt group stack sizes after they get refilled a few times. I had it set to 100 but they would only pick up one stack at a time most of the time, though they had 100 bolts at a time before.
The hunter should have a quiver and a crossbow. Once the bolt groups are filled (bolts will be listed in the rightmost panel) - pause and disable the hunting labor on your hunter, then unpause briefly, once the hunter is heading to the weapon stockpile to drop off their weapon, pause again and re-enable hunting. The hunter should drop their crossbow off in the weapon stockpile, pick it back up again, and then go get some bolts and go hunting. Each time they run out of ammo, repeat this last step.
Bolts purchased from a caravan, and bolts that belonged to a deleted bolt group, will never be reassigned by the arsenal dwarf. Consider them useless for hunting.
I tested this carefully but may have missed a step, let me know if this doesn't work for you.