My son put the cocking bolt together before attaching it to the gun. We can't get it apart! Do you have any ideas or do we have to get replacement parts?

Warning 1: this is a procedure for adults, not children - you may accidentally stab your own fingers.
Warning 2: this procedure might ruin the cocking bolt completely.
You'll need a small phillips head screw driver, two small flat-blade screw drivers, dental floss and four hands.
1) One end of the cocking bolt is fixed - leave this alone.
Remove the two screws from the inside face of the rotating end cap - this allows the outer cap to be removed.
The inner cap (still on the bolt) has four teeth that protrude into a recess around the metal bolt.
Warning 3: be extremely careful during the next step as the teeth may snap off completely and fingers could get hurt.
2) Using one of you four hands, hold the bolt upright on a sturdy table (with the fixed cap down) .
Simultaneously use the two flat-blade screw drivers to carefully lever one pair of opposite teeth out of the recess.
Whilst holding the levered the teeth out, firmly push the inner cap further down the bolt (down toward the fixed
end).
3) Wrap dental floss (or similarly stout, fine cord) around and around the recess to pack it out until it is flush with the outer diameter of the metal bolt - this is to stop the teeth locking back in place.
4) Slide the inner cap up and off.
Reassemble the cap.
Remove the dental floss.
Remind your son about the importance of reading the instructions first (just as you've always done yourself ;-).