Thanks very much, that is very useful. The more reading I do, the more convinced I am that it is not the Prvi Partizan ammo or the barrel twist, which is correct for the 9.3 - it is just a badly shot out barrel. I will go ahead with the G&H refurbishing plan and put up some before and after photos when the work is finished (probably 6 months to a year).

Thanks to all for your comments, much appreciated.