15mm blued barrel manufactured in the Czech Rep (same as S200)
Barrel fits into a brass O-ring carrier and only 1 grub screw locates the barrel. 2 others bear on the brass carrier
If the brass carrier is not a very good fit and not lock tighted to the barrel then the barrel can move around if shot fully floating with accuracy issues
Mk2,3 & 4 all have same action with a nickel plated 14mm Lothar Walther barrel.The action block is also different to that used in the Mk1's
The barrel location in the action block in Mk2-4's is better engineered than the Mk1's and these later Mk's shoot very well with the barrel fully floated. The fully floated barrel does help overcome POI changes through the charge
Most of the LW barrels are good.
Only some of the Czech Rep barrels are good
Stock changes were carried out to the Mk2-4's Not major