If Nerf Hyper rounds are 13-14mm diameter, then it stands to reason that with minor modifications the Sportsman would be able to fire them. With a massive hopper it may make for
Amazon.com: NERF Hyper Siege-50 Pump-Action Blaster, 40 Hyper Rounds, Holds Up to 50 Rounds, Glasses, Up to 110 FPS Velocity, Easy Reload, Toy Foam Blasters