The FX slugs slide right out the magazine . They are .216” . I tried some NSA .217 and they stayed put but just barely. I have ordered some .218” which I think will be the ticket. Don’t know what the barrel measures out at as that is very important too. You could still load the .216 and .217 slugs in the magazine from the front like you do on the Umerax A6 . The steel magazine clip would keep the slugs from falling out the back. Then once the magazine is in the action the slugs can’t fall out. Just because they are somewhat loose doesn’t mean they won’t be accurate. My Umerax K500 Huntmaster is very accurate with any slug and most pellets I put in it and they are very loose fitting by design because you have to load them from the front so don’t think the ammo has to fit the cylinders exactly to be accurate. As long as the cylinders index with the barrel And most important the ammo is sized properly to the bore the ammo will center itself with the bore . It has no other way to fit. I haven’t increased my reg pressure yet which will be required to push slugs fast enough so I haven’t tried shooting them. Still waiting on Ed to make the video on tuning the Leshiy 2. I can’t help with the .25 but I do have the .30 barrel kit and the NSA .300” slugs fit snug in the cylinder. I haven’t tried them either because I’m waiting on Ed to make the video on how to tune the Leshiy 2 . Oh did I say that already