There is a definite difference between the 7J German home market version of the rifle and the UK/export 16J/23J version, with the 7J version using a shorter stroke piston via a longer latch rod and a 2.6mm transfer port. The UK version also retains the 2.6mm transfer port as standard.
My information on the 23J version comes from friends in South Africa who have reported that the only difference is the spring and the 3.2mm port as standard. They have substituted a 16J spring instead and got excellent results from their guns. They did mention as well the 23J version felt harsh and oversprung by comparison.
Last edited by Dale; 14th November 2014 at 08:53 AM.