Speed measurement with Magnetospeed

Measuring muzzle velocity is a basic and essential activity for precision long-range shooting. And not only when reloading where speed measurement is absolutely necessary to find suitable loads. But also for creating ballistic charts for long-range shooting. In short, we cannot shoot precisely without speed measurement. And one of these methods is to use a Magnetospeed device. What is the practical experience with it?

Magnetospeed is a device that attaches to the barrel and measures the muzzle velocity of the projectile using an electromagnetic sensor. In the picture above, however, the sensor is not attached to the barrel, but to the forend and does not touch the barrel.

In this picture the sensor is attached directly to the barrel using tape. This is how it is supplied by the manufacturer. However, one of the basic lessons of precision shooting is that the barrel should be "free-floating" and should not touch anything... (LabRadar for measuring speed is also in the picture. I've done an intensive comparison of several types of devices, but I'll talk about that next time)

So the important question is: does mounting the sensor directly on the barrel affect the measurement, or the result on the target?

So I made a direct comparison to confirm (or refute) the theory that Magnetospeed affects target hits.

I used this weapon, which is the Ultimatum Deadline in caliber 6mm Dasher. It is currently my most accurate and reliable weapon designed for DPS (Dynamic Precision Shooting) competitions at distances of up to 1,000 meters.

I used two different types of ammo. They differ in bullets. In both cases, these are top loads and I wanted to confirm and verify that the load is still performing...

I performed the test at an indoor shooting range at a distance of 100 meters sitting behind a bench. Temperature was 20°C, pressure 968 hPa, humidity 55%. The series were 5 shots and between the individual series I had a break of a few minutes, when I alternately installed and removed the Magnetospeed sensor. The breaks were practically the same. The firing rate is approximately 30 seconds per shot. I was not in a hurry or stressed. The conditions were really "laboratory"...

5 shots with a Berger 108grs VLD Match.

The sensor is installed.

Average speed 882 m/s, ES 2.4 m/s.

It is worth noting that the cold bore shot is one of the three that touch.

Same charge 5 rounds.

The sensor is NOT on the barrel.

0.23 MOA.

5 shots with Hornady 110grs A-tip.

The sensor is installed.

Average speed 870 m/s, ES 1.7 m/s

Same charge 5 rounds.

The sensor is NOT on the barrel.

0.24 MOA.

Given that the result was practically the same with both types of loads I dare say that this result is trustworthy. And it shows that the Magnetospeed sensor installed directly on the barrel negatively affects the impact on the target. It is an expected result but it is still good to see it in practice.

In reality, this means that with the sensor attached directly to the barrel, it is not possible to measure speeds and evaluate the result on the target at the same time. As in this case, it is necessary to do a series of measurements and then another series to verify the variance. Magnetospeed measures very well and accurately, but this can be quite a disadvantage.

However, I also found it interesting to find out how these groups of hits overlap if we compare the target with and without a mounted sensor.

Loads with Berger 108grs VLD Match bullet. The upper target is with the sensor attached and the lower is without it. Several hits with the sensor are in practically the same place as all hits without it.

The same comparison of targets with a Hornady 110grs A-tip. Again, there are several hits in the same place as the target without the sensor. This was quite an interesting finding for me...

A way to avoid this effect on accuracy is to have the sensor mounted not on the barrel but on the forend of the weapon. The barrel simply has to be free from other objects and must have a free oscillation - as in the opening picture.

We have a sensor placed this way on this weapon and the control unit is attached to the weapon too, so the whole set of Magnetospeed has become almost "part of the rifle"... This rifle is in caliber 37XC and the ammunition is with the Warner Tool 361grs Flat Line projectile.