That Hellqvist sight is pretty funky to install - on the one example that I have here, it appears that the mounting holes are drilled and tapped vertically into the curved top surface of the rear bridge - off centre to the left and the right - but the sight is adjustable for both elevation and for windage. I got one on an 8x57 rifle from TradeEx - swapped that barrel to a decent 9.3x57 barrel that I wanted with aperture sights - seemed to work out okay. I do like the idea that it is contoured to match the rear face of that Swede stripper clip ridge - so one can retain that and load with stripper clips, if inclined to do so.
Apparently like 1920's all over again - 250 something or 280 something grain bullets - at circa 2,000 fps - stripper clip loading and aperture sights - all set to hit the bush and get a moose. In my case, it is using 285 grain lead cast bullets and fired at gophers in a pasture - I like seeing big gouts of dirt fly up - hit low and often the shrapnel will do the deed on the gopher(s).