How to change the scope? (S.T.A.L.K.E.R.: Call of Pripyat)

Hello! I have a question: How to change the aiming crosshair? I watched the video, where the obozorom builds. And builds sight was round weapons at all, not in the form of + (do NOT mean the optics). Want to do the same in Call of Pripyat. The texture of the circle I have, but it works only on the grenade, binoculars and bolt. If someone tell and teach - I will be grateful!
Thank you!!!