Sovereigns' were basically the british version of the Sniper/Autococker and were originally manufactured by the same lot that did the Sterling.
Sovereigns' take Sovereign barrels.... but you might have a spyder barrel adapter, in which case they'll take Spyder barrels.
If its a Sovereign I, try speaking to Powerball to get it traded up to a Sovereign II which are suppose to be quite good..
Why you bought it? Well, its your money...
Hope that helps
Ray