Somewhere around the mid- or late first century AD, the weighted pilum shows up. None have been found by archeologists, yet, but what we see in artwork is a regular tanged pilum with a ball behind the junction block. We are guessing that this is a lead weight, to add penetration power to the weapon since it had been getting progressively lighter over the years. The weight does not form part of the actual joint between iron and wood but is just below the joint. It might have been held in place by a cord wrapping on the wood below it, but there could easily have been some sort of nail or rivet holding it in place. Since the wood shaft was under an inch thick by that time, the weight didn't have to be very big, maybe tennis-ball sized or less. Though there is a tombstone from the late 2nd or early 3rd century that shows a pilum with TWO weights...