Ammunition

Chronographs: Types, Uses and More

radar chronograph

Knowing the actual velocity of your specific ammunition out of your actual firearm can be very useful. With that data, you can tell:

  • How much drop compensation to dial in at a long-range.
  • What power factor you have for IPSC.
  • Which load develops higher velocity in your particular gun.

For example, 100fps deviation from nominal velocity listed on the ammo box can mean a foot difference in drop at 500 yards. Different brands of .357 Magnum 158-grain ammunition can result in between 1630fps and 2250fps from the same 18-inch carbine.

Counter-intuitively, the lightest 110-grain can actually be slower than the top 158-grain. So, how do you know the true velocity of your ammo? With a chronograph, of course.

firearm velocity

What Are Chronographs?

The oldest chronographs date back to the 1890s. Greatly improved variants are available today from several makers. They all measure velocity by registering shadows from bullets across optical sensors, then comparing the timing between the front and the rear sensors.

They work very well outdoors, but can be rather more difficult to use in dimly lit indoor ranges. There’s also a constant danger of hitting the sensor themselves, as the bullet must pass within a foot or so of them.

chronographs

Types of Chronographs

Two competing concepts have recently appeared. The first is radar, represented by FX Airguns (for air gun pellets and bullets under 1000fps) and LabRadar (for all firearms).

chronograph measurement
Somewhat more expensive than the shadowgraph type, they require next to no setup and work in the dark, if necessary. FXDevices work with a cell phone app and can announce results with a voice, as well as show it on the screen.

shadowgraph
The third type, magnetic, works by registering the magnetic field distortion caused by bullets passing past sensors mounted on a plastic cantilever. This method is also independent of any light source, permitting indoor testing.

magnetic chronograph - magnetospeed
The chronograph sensitivity can be tuned to match the mass of the load in use. The setup is simply attaching the sensor pilon to the barrel, making sure it is parallel to the bullet path.

It can be tricky to produce correct alignment and offset of the sensor, especially with tapered barrels or integral bayonets. MagnetoSpeed works well with shotguns and rifles, but will not fit most semi-auto handguns.

radar chronograph

What Chronographs Tell You

All of these devices will save and aggregate ballistic data, allowing to determine velocity spread and standard deviation (SD) from mean to better judge the consistency and the performance of various loads.

For example, testing Seismic 185-grain plated hollow point, I got an SD of seven, a terrific result. Old Chinese 7.62×39 surplus has an SD exceeding 100, a clear indication of either poor quality control or improper storage—both good reasons to discontinue shooting it.

With a chronograph, we can also find out if a particular rimfire load breaks the sound barrier or not, thus predicting its noise level in a sound-suppressed firearm.

radar chronograph
Both for handloaders and inquisitive shooting enthusiasts, chronographs can be very useful.

Do you use a chronograph? Let us know your thoughts in the comments below.

The Mission of Cheaper Than Dirt!'s blog, The Shooter's Log, is to provide information—not opinions—to our customers and the shooting community. We want you, our readers, to be able to make informed decisions. The information provided here does not represent the views of Cheaper Than Dirt!

Comments (3)

  1. I encourage every handloader to get a chronograph to learn how a particular load behaves in a specific firearm for practical reasons or simply for fun. For example, in an effort to find 9mm Luger loads that would enhance the sound reduction of a suppressor, I “downloaded” several batches with progressively less powder. Then, I tested them with my chronograph to find what load would be subsonic, but still have enough oomph to work the semiauto pistol’s action. You can also experiment with (for example) 115-, 124-, and 147-grain bullets to develop loads where heavier bullets are faster than lighter bullets. With my chronograph, I get so much more from my range time than just punching holes in paper!

  2. I have usesd a ProChrono for several years. For my purposes it is cost effective. I use it to chronograph my pistol reloads and to check the “true “velocity of factory loads throught my handguns and rifles.

  3. I use the baseline caldwell chronograph. Bought some extra rods and sunshade from their website. I have found it accurate and reliable. Also, tough as nails. The front is currently wrapped in mossy oak duct tape after receiving a direct hit from a barnes 300 grain tsx in .458 ( at 1810 fps). I reset the chrono and it kept on working even with a sizable hole through it.
    It is a must have for reloaders. The book velocities are A: just what they got from their barrel in their test lab. B: A starting point.

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