the Anschultz and Hammerli rifles are the tools of choice for most of that kind of shooting.
Anschutz 1827, yes....frequently with a lighter custom stock. Hammerli, as far as I know, has not produced a Biathlon rifle.
The other popular rifle is the Russian Ishmash, also frequently custom stocked.
Both of these rifles use a straight pull bolt. The 1827 is a Fortner SPB. The Ishmash, which I have not handled, is similar and appears to be a clone.
The operation of the Fortner bolt is, indeed, very fast. One places one's thumb on the rear of the bolt, lifts the trigger finger to contact the bolt handle, rotates the hand backward at the wrist about 45 or so degrees, the bolt opens, cartridge ejects, thumb pushes the bolt close, finger drops to trigger. As fast as you can move your hand back and forth. The trigger is about two ounces. If so desired the rifles could be shot about as fast as a semi-auto.
Aperture sights - snow sights - both the rear and the front have integral flip up covers to protect the sight from falling snow. The front sight also protects the muzzle.