I drilled and tapped one screw hole on the barrel boss just ahead of the receiver ring and one in the 'blank' drifted into the raised rear sight boss of the CZ Hornet barrel I screwed into the action. I used a Weaver base, drilled a new hole as necessary. IIRC - I used 8x40's because there was only two of them - that was for the .22 Hornet.

On the .17HMR, I drilled and tapped 3, 6x40 holes into the barrel, in a flute, again using a Weaver base.