There were some interesting observations today with the Magnetospeed and harmonics. A tall target test was the intent to check tracking of a newly installed ATACR on a TRG-42. A Magnetospeed was attached for MV verification a fraction of an inch in front of the muzzle brake. After a few shots and a solid zero the Magnetospeed was moved another inch away from the muzzle brake. Another shot was taken to verify the zero. This shot was approximately 1” high. MV was not out of the norm. Two additional shots were taken showing a less than .25” group. Moving the Magnetospeed one inch caused a difference in harmonics to produce a 1MOA difference in grouping. The Magnetospeed was removed and the following group was just over 1.5 MOA low. I would not have guessed this one. The tall target test was conducted without the Magnetospeed. ATACR tracking shot groups produced a vertical spread of 31.5” with 30MOA dialed. I enjoy the benefits of the Magnetospeed. IMO, final load development is best suited without the chronograph attached to the barrel with potentially MOA plus change in POI to POA with little displacement or complete removal of the chronograph.