i have just bought an old s400 classic and it is faultless.i was always sceptical about air strippers but gave the rowan one a go and after a lot of adjusting it has tightened up the groups to an almost unbelievable level.
mine works best filled to 160 and shot down to 110,i get about 50 shots out of it.i can hit 15mm spinners at 50 yards with ease.