For muzzleloaders, I believe its Circlefly that makes a wad that will tighten up those cylinder bores. How they work is; the plastic cup is just that a cup which has to have its sides cut vertically producing custom length petals. The length of the cut produces a more 'Open' choke. However that's in a muzzleloader where you don't have a chamber to deal with I've never looked to see if they make them for modern reloading. That could be worth checking into.