Try to get the absolute minimum of lubricant in front of the seal to minimise dieseling. You may then be able to let the new seal 'wear in'. Your kit...
Just to update and inform everyone who is following this thread, I have found nothing wrong with the new steel piston supplied to me by TW Chambers....
At higher speeds the pellet will cut a smooth clean hole straight through, & exit taking much of it's energy with it.
At slower speed will smash in,...
They reckon that engineers during the wars were the least effective fighter pilots.They tend to ‘nurse’ the aircraft rather than chuck it about most...