You don't need a chronograph to get zeros at different ranges. Regardless of the group size you shoot, just get a zero at different ranges. Then write them on a label that ends up stuck on your scope.
If you use two different loads, you'll need two different labels; put on the one that matches your load. You'll also need different labels for the same load when used in different ambient temperatures and elevations. Keeping a log for different condtions and loads will help establish really accurate zeros for each.
US Navy Distinguished Marksman Badge 153
Former USA Palma Team Member
NRA High Power Long Range High Master
NRA Smallbore Prone Master