hi guys,
intresting read this thread lots of things been done and tried but no mention of triming to lenght,
would seriouly suspect that the cases need trimming to lenght espicially as been used in a different chamber.if long in the throat you may get away it but seems your new howa has a tight chamber so case pinching bullet during expansion backed up a bit as new factory ammo which is to lenght works ok the ordering of new brass will cure the problem until case lenght grows again.
graham.