I was wondering, are CZ550 magnum bolts the same as a Brno 602? Will one fit the other? Reason I ask is that I have a new Brno ZKK602 bolt with 3 position Wisner safety and was wondering if it will fit a CZ550 magnum if I get one? Are they interchangable. (apart from checking headspace of course)

Superficially they are the same except for the cocking piece and shape of the bolt handle.

I have the same situation as you.

Trying to interchange the bolts on my two: cannot even slide the bolts far enough in to begin to turn down the handles on either one.

Also the sears differ by about 0.003" in longitudinal length.

The fitting of the 3 position safety is a meticulous thing involving machining fixtures and less than hairsbredth tolerances in engagements.

Start from scratch with the safety parts for another one, and a gunsmith.

I haven't done such work but rely on a competent gunsmith. I wouldn't think about swapping bolts, or reusing the safety parts from one on another rifle ... it might work if the switch required extra metal taken off, but it is tough to rebuild and re-machine that kind of part.

Oh ,well ,I was hoping they would be interchangable ,but it looks like it Isnt so. Thanks for the info.