Check out the Guiard Tool annealing machine. It is excellent and is not very expensive. The Guiard was the first annealer I purchased and still have, but I also have an AMP because I do so many different cartridges.
The change is negligible plus you are only using the Chronograph to find muzzle velocity and SD flat spots. When you move to final load testing you will have a set load and just look at effects of OAL on the group. Magneto Speed is the best and I have a Lab Radar and standard shoot through...