Hi Badger,
I would say that you had a faulty BSA rifle if it was grouping like a shot gun mate.
Every BSA pcp that I have ever shot were deadly accurate and if matched with the correct pellet will put a pellet on top of a pellet at 40 metres easily enough and even with my average shooting skills.
I shot Andy&Archie's .22 r10 about 3 weeks ago with Falcon Accuracy Plus pellets and did a 10 shot 1 hole group with un sorted pellets at 30 yards that was covered by a 5p coin. This 10 shot group was with a straight out the box r10, i.e not tuned or customised.
I then shot a 10 sh