As the title suggests, what’s worked for you owners? I have the bottle version with a 500mm barrel. It will have high flow probe and dual port with middle bracket to prevent tumbling. I’m thinking 21-23g stuff. Not to keen on fx hybrid slugs.
Nielsen Slugs work amazing in my 500mm Wildcat Tube version. I have been using the 17.5g in several rifles, and they are awesome. Great accuracy and lots of punch for bigger pests. The 20.2 grain are also supposed to be exceptional but I have a big pile of the lighter ones to go through first. I have a regular STX Superior liner too and they are easy to get good speeds out of even with a mostly stock rifle. No problem pushing them 950-1050fps, especially in a Wildcat BT.
Try Daystate Howlers, made by NSA. I believe they're .217. I'm shooting them out of a borrowed Edgun with extreme accuracy. The Nielsen .2165's not so much but the .217's are Nirvana! AoA has them.