New silencer

Hi guys, Im currently making a new silencer for my storm and I need some advice. I’ve drilled the center hole at 6mm (obviously .22 pelet is 5.5mm) and now I have done this Im wondering how the pellet will travel down through it Ie is the gap too big, too small? Im sure some of you have made a silencer so any input and do’s and dont’s would be apreciated.