I want to convert a VZ-24 action to 8-40(from 6-48) thread for mounting the scope base. Doing the action appears straight forward - drill out the hole and re-tap.

What about the base(one piece Leupold)? Am I correct in assuming that the counterbore Brownells sells can be used for this conversion?

Counterbore tool

I beleive it will work IF the pilot section is long enough to have good bearing in the screw size clearance hole you will drill in the base. The pilot on the one I own is only .216" long, which is kind of short. A 1/4" machinists counterbore with interchangable pilots, which may be longer, may work better, not sure. Good luck with your project. Joe

Mauser 98
I do this conversion frequently and the 8-40 Fillister counterbore that Brownells sells is fine. You have to enlarge the holes in the base with a #21 drill to allow the pilot to enter the hole then counterbore until the head is at the proper depth. Then enlarge the hole to pass the 8-40 screw. The clearance drill for that is a #16. You can do it faster than you can describe it. have fun. Jerry