It might not be the mount, could be the stock bolt tension, stock to action fit, how you put the gun in your shoulder, temperature, dodgy scope, underlever fit, relative position of Jupiter to Earth, moon cycle, tidal system, state of tune, air density etc
Ask RobF about zero shift on a HW97k. Some just seem to shift and others don't.
I popped mine away in August, and got it out again this weekend. It needed 16 clicks elevation and that's the first time I've seen it shift.