Board Thread:Questions and answers/@comment-46.116.168.150-20130615113345/@comment-23891957-20131009062235

Some people add Reactors to the bottom of barrel extensions to act as "grenade launchers." Although this isn't a solution offered by Nerf (and it sacrifices a tactical rail) it shows that it has been done.

Although, I bet a homemade ball launcher powered by HPA would be interesting to see. Maybe you could stuff two or three in the launcher and have it be like a sort of grenade-shotgun launcher.