Bought a brass UK Neil stripper 2nd hand. Put it on a mates 400 which grouped well with a silencer and couldn't get it to group no matter where it was set. Put silencer back on and grouped well again
. Sold it on to a club member (told him why I was selling) and it improved his groupings (cone set approx. 1 pellet llength away from barrel). Had a GML at the time which started throwing fliers, found to be clipping the GML stripper. Had a brass one made by Elmor Fudd, non adjustable, and it grouped very well. Maybe it's down to the weight, where the cone is positioned or it's psychological, who knows. One thing for definate is that if not fitted correctly it can make things alot worse, whether it improves things is debateable.