Watched a YT vid from a guy from England talking about how to get more precision from your springer. Noticed he had something rectangular-ish attached to his barrel just behind the muzzle. In the vid he explained and described his gun and why each component was their. the barrel thingie was 180 grams of stick on wheel weights. Guessing it was to slow muzzle movement and help mitigate recoil. Read and reread the WFTF rules.... couldnt find any mention if allowed or not.
Not sure Id add anymore weight (it would have to be an appreciable performance gain) to an already heavy rifle, even if allowed