Scot’s Product Review: MagnetoSpeed V3 Ballistic Chronograph


One of the most basic needs for all living creatures is the ability to defend themselves. When there are bad times and problems in our society, it is essential to own and be able to use weapons for self-defense. The situation could be a regional disaster, like Hurricane Katrina, or it could be the worst of times, such as a Carrington or EMP event. In either case, there are wicked people who will take advantage of those who are weak. Even if you can avoid evil people, there are predators to be dispatched and game to be gathered for the table.

Having weapons is not enough. We must have skill with them. That means training and practice. Both require ammunition, and that stuff is expensive and sometimes hard to acquire. Being able to make our own by recycling cartridge cases saves money and also provides more detailed knowledge of how our weapons work, which is a component of being skilled. Reloading also allows us to tailor ammunition to specific purposes, from practice to self-defense and for hunting specific game animals or predators.

A key consideration in having ballistic success with our ammunition is how fast the bullet is going and how consistent the velocity is from round to round. That’s not something we can eyeball. While we can obtain some data for factory specs or from reloading manuals, the only way to know for sure what we are getting is the use of a ballistic chronograph– a device that can measure and record bullet speeds. While you can do okay without one, you will have far more data to work with as you tune your ammunition to your weapons if you have access to a chronograph.

At one time chronographs were rare and expensive, but thanks to modern electronics that has changed. In the early days of measuring bullet speeds, a number of approaches were used, such as a pendulum or a moving piece of paper. By knowing how far the pendulum swung when struck by the bullet or how much the paper traveled while the bullet was in flight, we could calculate its speed with reasonable accuracy. Today, however, chronographs use sensors that can detect the bullet as it passes over them. The timer starts as the bullet goes over the first sensor and then stops as it passes the second, and a computer determines the speed. Some add extra sensors to double check accuracy.

The most common form of sensor reacts to the shadow cast by the bullet as it passes over them. The bullet needs to pass directly over the sensors and its path should be parallel to them. There is often a diffuser placed over the sensors to provide even lighting. Sometimes, however, differing light conditions such as the lack of a good shadow or angled light that places the shadow offset to the sensor can cause problems and errant readings. Indoor lighting can be problematic for some sensors, particularly under lights that flicker, as most fluorescents do. The sensors usually need to be placed at a set distance in front of the shooting position. If the sensors are too close to the muzzle, blast can affect readings. The shade assembly typically forms a “target” area for the shooter to aim through to record results. There is the problem, however, of accidentally shooting parts of the unit, especially when testing weapons with a lot of sight offset, like the AR-15.

A newer and different form of sensor is found in the $399 MagnetoSpeed V3 Chronograph , which uses the disruption of magnetic fields by the bullet’s flight to measure speed. I was baffled a bit about how bullets made of non-magnetic materials could be read, but the physics work despite my inability to fully grasp them. The sensors are contained in what MagnetoSpeed aptly calls the “bayonet”, which attaches to the weapon’s barrel.

Putting the bayonet on a weapon the first couple of times is a bit fussy. It has to be positioned so it is parallel to the bullet’s flight and not in its path. It is recommended to have a .25 inch gap between the bottom of the bullet and the top of the bayonet, though air rifle pellets may need a narrower gap. In any case, you want to make sure the bullet does not hit the bayonet. However, unlike the down range sensors, once it is set up there is less chance of a brain fade and a hole in the sensor, since it stays fixed in relation to the bullet’s path. If you set it up right, there won’t be any problems when you get tired and lose a little concentration. Most of the time, we will place it at the bottom of the barrel, but it can be placed at any orientation to the bore.

You get a supply of spacers and shims to align the bayonet. What makes it fussy initially is that the shims compress as you tighten the assembly to the barrel. As you get used to how much they compress, it gets easier to pick the right one to start with. If you are smart, you will also take notes about which spacers are needed for which weapon so you won’t have to experiment the next time.

When you attach it to the barrel, you pull a mounting strap tight and then twist a knob to ratchet it tighter so it is securely mounted on the weapon.

A slight amount of barrel taper can be accommodated with the existing shims. If there is much, they sell a kit with special shims for $4.99 that allows you to correct for it.

MagnetoSpeed provides an alignment guide to help you get the gap between the bullet path and the bayonet correct. A cleaning rod will help too, as noted in the instructions. Just insert the rod in the barrel to show exactly what the bullet path will be and then use the alignment guide to be sure you have the right gap. The cleaning rod would need to be as close to bore diameter as possible, of course.

The V3 I am reviewing can fit on a barrel or suppressor up to two inches in diameter. There is a heat shield to be used with suppressors that can get very hot.

A new version is coming that will be available at a lower cost, but it only fits barrels up to one inch in diameter. It will have a fixed cord and won’t be able to tolerate as wide a range of muzzle devices.

The unit comes with your choice of a hard or soft case. The review unit I received had the sturdy, hard polymer case with neatly cut foam inserts for the unit and accessories. You get everything you need, including a battery and an SD storage card to hold your data, which can then be transferred to your computer. There are even two sets of cables to connect the display unit to the bayonet, and they are long enough to do the job. One is retractable, and they use a standard connector, so should you break or lose one it will be easy to replace it. The instructions are clear and easy to understand. Everything looked professional and well made. The only thing I would have wished for was a spare set of screws for the bayonet mount. I have a vivid vision of one of them popping out of my fingers and bouncing out in front of a bench at the range where I can’t get to it. You can order a spare set for $3, if you wish.

The whole kit weighs only about 2.6 pounds, and the storage case is 10×13.5×3.5 inches in size. It is made in the U.S. with some foreign components. The bayonet adds about 8 ounces and 11 inches to the muzzle of the weapon. I discovered it is very magnetic when measuring it, so you might not want to get it close to your watch.

The instructions are quite clear and comprehensive, though I was horribly fuddled at how to turn it on until I realized that it turns on when you plug the cable into the top of the display unit. Sometimes the simpler it is, the harder I have to work!

I was a bit surprised that, as well as rifles, they recommend it for shotguns. I hadn’t thought much about this and would never try shooting a shot load through a sky screen style chronograph. However, since a shotgun pattern doesn’t begin to spread until it is downrange a few feet, all is well with the MagnetoSpeed as it is located at the muzzle. They do have some guidance in the instructions on fitting with shotguns.

It works well with revolvers that have enough space to mount it on the barrel, but semi-auto pistols are generally a problem. The strap that wraps around the barrel to hold on the bayonet will cause functioning issues with most self-loaders that have a reciprocating slide. MagnetoSpeed has developed a $25 rail mount that will work with many weapons that have rails for mounting lights or accessories, though they warn it will not work on all of them.

The small display unit takes either a standard 9 volt battery or two CR123A batteries. I like the option of battery choices and was especially happy that it will use a very common and widely available battery, though the CR123A’s will provide a longer run time.

To use it, you simply connect the display unit to the bayonet with either of the included cords. I preferred the retracting one, as it meant less wire to get tangled up. Delightfully, the connectors are common stereo microphone ones, so if you lose or break the cable, you can get a new one at Radio Shack. There are two connectors on the bayonet for the cord, so you can connect it to the back or bottom as your needs require.

There are a number of functions available from the display unit. Archiving a shot series allows you to save it to the included SD card, which can then be removed to transfer the data in the form of a spreadsheet file to a computer. You can continue to view any data that is on the card, though you can’t add more shots to a series that was archived. You can delete a shot or a whole series of shots. You can adjust sensitivity of the sensors, which might be necessary for use with smaller, lighter, or slower projectiles, particularly for air rifles.

It’s interesting, though not much use to me, that there is a rapid fire mode that MagnetoSpeed says can handle up to 1,100 rounds per minute. I have no automatic weapons and no access to any at the moment, so I didn’t get a chance to check this function.

I found the display easy enough to read, since it can be placed close to the shooter. The base is angled up, so the screen is at about a 30-degree angle towards the shooter. It can also sit so the screen is straight up if that is more convenient. There is a backlight that makes the screen much more visible in low light but at the cost of battery life. You can switch it on or off as needed.

You can be metric or English for velocity and have it display standard deviation or extreme spread on the home screen. Both statistics are kept when a shot series is archived.

MagnetoSpeed warns on their website that your group placement may change when you hang the bayonet on the muzzle; this was something I expected. They say that group sizes usually aren’t affected much. I found this generally true, though I spent most of my time working with an air rifle and an AR15 with relatively stiff barrels. I suspect that there could be changes in group size with many weapons. However, since I prefer to separate accuracy and velocity testing, the question of accuracy with the bayonet attached doesn’t matter to me.

I find it amazing that the unit can measure a bullet’s speed over the 5-inch distance between the two sensors on the bayonet.

I have some concerns about muzzle blast eroding the bayonet, but I haven’t seen any problems. A friend owns one with quite a few rounds through it, and his looks fine. There is a metal shield facing the muzzle to protect the unit.

For me, the biggest advantage of the MagnetoSpeed is that I can use it on indoor ranges. I have yet to find an indoor range that will allow me to setup a conventional chronograph in front of the bench, but I have had no issues using the V3. There have been no problems with the low light that is often used indoors or with flickering fluorescents. It is also delightfully easy to archive data, which is something I can’t do with the older unit I often borrow.

Overall, I am very impressed with the V3 and am scrounging for funds to buy one. My only complaint is not being able to use it with most semi-auto pistols or short barreled revolvers. My friend is pondering building a jig for his to hold the bayonet and align a 1911 properly, which would take care of most of my issues. Truthfully, however, most of my need for measuring velocity is for centerfire rifle ammunition to confirm what I am getting in real life. For that, the V3 is a blessing.

Work Sharp Update

We got a nice note from Holly Deffenbaugh at Work Sharp with a good explanation about how to avoid rounding the tip of a knife with their sharpening tool. I reviewed it originally last September and then updated it at the bottom of another review when I discovered that careless use can round blade tips. As with any sharpening tool, you need to use it correctly. Here is Holly’s note with some good pointers on using the Work Sharp properly.

“Hi Scot. Thanks for your update on the blog about the Work Sharp Knife and Tool Sharpener. Rounding off the tip of the knife can be a common problem, but as you said, with a careful finish through you will avoid this. Our suggestion to users is that you pull the blade back briskly while keeping your arm straight. Once you get to the tip, do NOT slow down. The faster the better. Also, don’t follow the curve of the knife, remain pulling straight or even at a downward angle. Keep the blade up against the guide at all times, but be sure that you are pushing with force against the belt. The belts are flexible and so they will give with your knife. If you push into the guide and belt with too much force, you can cause that rounding as well when coming off the belt with the tip.”

– SurvivalBlog Field Gear Editor, Scot Frank Eire

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