If your 916 still has the hole in the barrel where the bead was it's probably not a cut down. Many 916's were sold to LEO agencies. Frequently getting in and out of cruisers very often resulted in the loss of the bead. I've seen some officers take them out on purpose so the wouldn't hang up on something. Missing beads are very common to all riot guns no matter who makes them. I've had several replaced by a friend who has an assorted box full of them. He pulls them out until he finds one that fits. He recently replaced one on a long tube Ithaca 37 and replaced another on a 870 a while back.