not had the.177 but had the mark 1 in a .22, great rifle for bunny stalkin and stoggys so light and accurate too. the mark 1 and think the mark 2 also have a little grub screw allowing it to arond 22ftlb with half turn, obviously you wouldnt do this unless you had fac cos not allowed but if some one wanted to and marked clearly where to turn it back to when you had to its quite a handy tool out to around 60 yards on bunny.
......also if you rub the barrel gently whispering "perdante,perdante" a genie will appear.