condor ss cal 22 & 25 what slugmold will work ?

Ich have buy a Gunpower XS its a Condor ss in 22 cal and a UK brand.

This thing shots with his 18 inch barrel the

Jsb Heavys 1080 fps

Jsb Monsters 1020 fps

Jsb Beasts 920 fps

At full fill and lowest power settings

So far so good at close range to 30 yards the Heavys and Monsters are on point the Beasts groups bigger with half inch 

But i want to shot long range so i strech out to 130/140 yards.

The Heavys are very accurate when is no wind but the Monsters and the Beasts can be very dangerouse.

At this distance i have seen that some of them break out and hit the dirt more than 40 yards from the point of aim in any direktions

I think they start spiraling somwhere on their journey and loose total theire stability.

I what to order a 25 cal replacement barrel and to plink out to 200 yards with both calibers.

I need some recomandations from people who shot there own cast slugs with these rifles.

Thanks for all informations that comes inn here.