inner wall 17 forms a passage 27 that receives the end portion of the shaft 12 so that the chamber 20 surrounds the shaft and so that the end of the shaft abuts the wall section 16 b as shown the threaded male neck of the broadhead 13 extends through the hole 25 and is threaded into the end of the shaft 12 thereby securing the front wall section 16 b between the broadhead 13 and the end on the arrow shaft the capsule 11 is molded from a material such a polymerized styrene or the like that will fracture in one or more fracture zones formed in the capsule walls these fracture zones may consist of breakaway grooves molded in the walls in the illustrated embodiment a breakaway groove 31 is located in the forward end 15 of the capsule at the juncture of the wall section 16 a and the outer wall 18 so that the outer wall will separate from the front wall 16 in order to insure complete separation of the outer wall 18 from the front wall 16 the wall section 16 b may be made thicker for example twice as thick than the wall section 16 a and the.