- Location
- Somewhere on the Hudson Bay Coast
A little while ago I had the opportunity to try a chronograph called the MagnetoSpeed. Rather than working on the shadow of the bullet passing a screen, this one works with magnetic sensors attached to a plastic bayonet which is strapped to the muzzle of the firearm. The unit can be set for jacketed, mono-metal, or lead projectiles. I only shot jacketed across it, thinking that a very fast bullet would be the best test, so I measured 55 gr bullets from my .243 which are the fastest I have. I set up the test in such a way that the velocities were measured by 3 chronographs at the same time, The MagnetoSpeed was attached to the muzzle of the rifle, and 10 feet from the muzzle I had my Chrony set up between the screens of my Oehler 35P. The MagnetoSpeed comes with shims so that the angle and distance from the bore can be adjusted for a broad range of muzzle diameters and contours.
During the testing I became aware of some the advantages of the MagnetoSpeed. Its fast to set up, the sensors are always the exact same distance from the muzzle, the unit is not disturbed or distracted by muzzle blast or by particles of powder crossing the screens, or by ambient light, and it is much easier to shoot at a target downrange than with a chronograph that requires you to line up the firearm to the screens and the target. If there was a disadvantage to the MagnetoSpeed, it was that the "bayonet" had a tendency to slip forward with each shot, so after each shot I'd pull it back a quarter inch or so. Now I wish I'd tried it on a hard kicker to see if this movement became problematic. Because the unit attaches to the muzzle with a web strap, muzzle brake equipped firearms are set up slightly differently, but since none of my guns are braked, I didn't pay enough attention to repeat the instructions here.
I won't repeat the velocities I recorded, except to say that in my experience every chronograph is an individual, and no two will measure the same speed from the same shot every time. But out of 10 rounds fired, the MagnetoSpeed did measure one velocity the same as the Chrony, which was 58 fps faster than the Oehler claimed. The closet it came to the Oehler was 25 fps, while the greatest difference was 70 fps and a difference of 60 fps was probably average, with the Oehler always showing a slower velocity. The greatest velocity difference that was recorded by the MagnetoSpeed and the Chrony showed 80 fps, faster for the Chrony which may have been a hiccup as the other readings all had the MagnetoSpeed velocity higher except for one that was the same. The average difference between the MagnetoSpeed and the Chrony was probably 30 fps. Despite the differences in velocity readings, the measurments between the MagnetoSpeed and the Oehler were slightly more consistent, mainly due to the 80 fps hiccup with the Chrony.
Check it out with a Google search for MagnetoSpeed.
During the testing I became aware of some the advantages of the MagnetoSpeed. Its fast to set up, the sensors are always the exact same distance from the muzzle, the unit is not disturbed or distracted by muzzle blast or by particles of powder crossing the screens, or by ambient light, and it is much easier to shoot at a target downrange than with a chronograph that requires you to line up the firearm to the screens and the target. If there was a disadvantage to the MagnetoSpeed, it was that the "bayonet" had a tendency to slip forward with each shot, so after each shot I'd pull it back a quarter inch or so. Now I wish I'd tried it on a hard kicker to see if this movement became problematic. Because the unit attaches to the muzzle with a web strap, muzzle brake equipped firearms are set up slightly differently, but since none of my guns are braked, I didn't pay enough attention to repeat the instructions here.
I won't repeat the velocities I recorded, except to say that in my experience every chronograph is an individual, and no two will measure the same speed from the same shot every time. But out of 10 rounds fired, the MagnetoSpeed did measure one velocity the same as the Chrony, which was 58 fps faster than the Oehler claimed. The closet it came to the Oehler was 25 fps, while the greatest difference was 70 fps and a difference of 60 fps was probably average, with the Oehler always showing a slower velocity. The greatest velocity difference that was recorded by the MagnetoSpeed and the Chrony showed 80 fps, faster for the Chrony which may have been a hiccup as the other readings all had the MagnetoSpeed velocity higher except for one that was the same. The average difference between the MagnetoSpeed and the Chrony was probably 30 fps. Despite the differences in velocity readings, the measurments between the MagnetoSpeed and the Oehler were slightly more consistent, mainly due to the 80 fps hiccup with the Chrony.
Check it out with a Google search for MagnetoSpeed.
