Muzzle velocity is a critical component to plotting the ballistic trajectory of a precision rifle. It is easy to look up the dimensions and ballistic coefficient of the bullet you are shooting. However the muzzle velocity is unique to each rifle. You cannot rely on velocities printed on cartridge boxes or even the numbers your buddy gave you for his pet load. The easiest way to obtain an accurate muzzle velocity is to measure it with precision equipment. The Magnetospeed V3 Chronograph makes this a simple task.
Prior to obtaining a Magnetospeed, I would drag out my old optical chronograph. It would require that I set it on a tripod forward of the firing line and record the exact distance from the muzzle. I would have to setup the “sky screens” and hope for consistent lighting conditions. Clocking ammo at sunset was a no-go unless I bought lights for the unit. Accuracy could be affected by muzzle blast and more than once it was thrown off by an insect flying through the screens. This just touches on a few of the practical issues of optical chronographs. The technical aspects become even worse.
Precision rifle shooters use fairly pointy bullets. A certain amount of this bullet has to pass the sensor before it triggers. You have to hope that the same amount of bullet passes to trigger the second sensor. Due to the extremely short distance between sensors, the precision of this measurement is critical to the accuracy of the chronograph. The Magnetospeed V3 Chronograph removes all of these issues and more.
The Magnetospeed V3 is unaffected by light conditions. It is one chronograph that allows me to test loads in the dead of night (suppressed of course). This also means you don’t have to worry about that nice single digit SD you are working on getting blown away by a passing cloud.
I have been using the Magnetospeed V3 for more than a year now. In the past, chronographs were a chore and I would only drag one out when I was doing load workups. Even though the protective case for the Magnetospeed is twice as large as the cardboard box that holds my Shooting Crony F1, the Magnetospeed now accompanies me on just about every trip.
The Magnetospeed V3 attaches directly to the barrel of your rifle. This eliminates one of the major issues with chronographs: going downrange. Now you don’t have to ask the range to go cold while you setup, align and measure. You can setup and teardown the unit while other shooters are hot. Magnetospeed sends a number of spacers to accommodate most barrel diameters, including suppressors. A protective band to slip between the mounting strap and your suppressor is included, however high volumes of fire should be avoided. If you are on the opposite end of the spectrum and you are using very thin “sporter” type barrels, Magnetospeed has a tapered spacer kit for that purpose (additional purchase).
Setting up the Magnetospeed V3 is a pretty simple task. You stack spacers on the bayonet mount until the sensor deck is just below the bore line. Double check this with the included alignment rod and then tighten down the nylon strap. I prefer to perform one last check with the alignment rod and then sight through the bore before firing. Many issues shooters encounter come from not setting the spacing within the .125-.25″ that Magnetospeed recommends.
The polymer spacers have a indexing feature which prevent them from working loose under recoil. However it may be a good idea to use the included screws and secure them to the bayonet mount. Since we routinely swap the unit around onto rifles with differing barrel diameters, we don’t use the screws, but don’t blame us if you shoot a sensor.
Once you have the Bayonet Sensor mounted on the rifle, you will need to connect it to the display unit with the included 3.5mm connection cable. The display unit will automatically power on when the cable is connected. If you need to retrieve data from the display unit, you can simply plug in a 3.5mm cable without attaching the bayonet sensor.
The menu system is a simple combination of up/down buttons and a center select button. For most situations, the factory default settings are sufficient. The sensitivity may need to be adjusted for cartridges like the .22LR.
Once the unit is connected and powered on, shooting will cause each shot to be recorded. As your shots accumulate the display unit will automatically calculate your extreme spread or standard deviation (depending on your menu selection).
Once you are done with your string of fire, you can archive the shot series to the internal memory card. You can then start a new shot series.
The until is fairly straight forward to work with. We did find a couple of small issues that can cause some headaches. When you install the bayonet unit, make sure it is tight. Early on during our testing we did manage to skip a bullet off of the sensor deck. This destroyed the sensor. A replacement bayonet unit currently costs $169, so this is a costly mistake.
One other issue that we noticed is that the Magnetospeed is sensitive to the distance from the bore. It uses a disruption in the magnetic field to trigger and record a shot. The greater the distance from the bore, the weaker this disturbance is. The alignment rod included with the system is approximately 1/4″. The bore of the rifle should not be further away from the sensor deck than the width of the alignment rod. If you do mount the sensor further away, you will not get the best accuracy.
The last issue we have encountered seems to be rifle-specific. Since the Magnetospeed V3 mounts on the barrel of your rifle, it can affect the harmonics of the system. It seems to affect lightweight barrels more than heavy barrels. Our .243 with a Krieger #9 contour is not affected in any measurable way with the Magnetospeed mounted. My Wife’s Remington 700 with a varmint weight barrel will not shoot the same point of impact with the Magnetospeed mounted. It shoots fine as soon as it is removed. This is important to know for those of you who want to use the chronograph for load workups. It may necessitate running a separate string for velocity in addition to your strings for grouping.
After spending some time with the Magnetospeed, I can say that it is extremely easy to use. It is so portable that I rarely go to a match without it. While we lack the laboratory grade instrumentation necessary to test the precision and accuracy of the Magnetospeed, it has easily allowed me to gather the data needed to make first round hits beyond 1000 yards.
I want to thank Magnetospeed for supplying the V3 used for this evaluation. Additionally, Magnetospeed units have been appearing on prize tables at matches around the country. The team at Magnetospeed is a great group of guys to deal with and is dedicated to supporting the shooting sports.