A lighted nock assembly is disclosed for use with an archery projectile. A cap fits within the tail end of the projectile shaft. The cap comprises a shoulder to bear against the projectile shaft, a recess terminating in a floor portion, and a face to bear against the shoulder of a nock. An LED/battery assembly fits within the recess of the cap abutting the floor portion. A nock fits over the LED/battery assembly and into the recess of the cap. Ready-to-fire, the LED/battery assembly comprises an activation gap between the LED lamp and the body of the battery assembly. A gap, greater than or equal to the activation gap, is left between the shoulder of the nock and the face of the cap. When fired, the bow string drives an internal surface of the nock into the front end of the LED/battery assembly and illuminates the LED lamp.