Thanks for the responses! I am looking into the mauler valve link you sent me! Would like to shoot tennis balls. Not sure how to modify my rainbird sprinkler valve. It works pretty good....just makes a "honking" noise every time I shoot....is this is an indication of slow activation????

It appears that Spud Tech is no longer selling their SGTC Supah-Valve. Where can I purchase one of these? Not sure I have the "know-how" to modify...or make one. Currently using a "rainbird,3/4" in line sprinkler valve. Sounds more like an air horn than a gun. Suspect that it is not fast enough ...