NOTE (August 2020): Our inventory has sold out and we are halting orders for the time being in order to focus on AutoTrickler and ShotMarker production.
The Two Box Chrono is designed for one purpose: eliminating random error from velocity measurement.
Shooting tight elevation at long range is all about velocity consistency. If you shoot F-Class style competition and fire hundreds of rounds in load development each year, than this chronograph is for you.
I designed this chronograph after I realized it was necessary for load development. After firing a few thousand shots and struggling with repeatability, I learned how to apply statistics to my data in order to understand what was going on. It quickly became clear that without a more precise chronograph, measuring and tuning SD through load development is a complete waste of time.
Two acoustic sensors spaced 15 feet apart measure the time of arrival of the supersonic shock cone of your bullet. The Two-Box Chrono has repeatability error of 0.5 fps SD, or 0.02%. This will provide a level of consistency that will be a real eye-opener for serious competitive shooters that can take advantage of it.
There are no frills with this product. There's no Bluetooth, no SD card, no internet, and no mobile app. It doesn't calculate anything for you and it doesn't hold your hand. Just put the boxes on the ground, line them up as best you can, fire over top, and write down the number you see. It just works.
Shooting tight elevation at long range is all about velocity consistency. If you shoot F-Class style competition and fire hundreds of rounds in load development each year, than this chronograph is for you.
I designed this chronograph after I realized it was necessary for load development. After firing a few thousand shots and struggling with repeatability, I learned how to apply statistics to my data in order to understand what was going on. It quickly became clear that without a more precise chronograph, measuring and tuning SD through load development is a complete waste of time.
Two acoustic sensors spaced 15 feet apart measure the time of arrival of the supersonic shock cone of your bullet. The Two-Box Chrono has repeatability error of 0.5 fps SD, or 0.02%. This will provide a level of consistency that will be a real eye-opener for serious competitive shooters that can take advantage of it.
There are no frills with this product. There's no Bluetooth, no SD card, no internet, and no mobile app. It doesn't calculate anything for you and it doesn't hold your hand. Just put the boxes on the ground, line them up as best you can, fire over top, and write down the number you see. It just works.
Every shot, every time.
Highly sensitive acoustic sensors detect every shot over 1250 fps and are not dependent on sunlight or weather conditions. |
Alignment made easy.
Use the magnetic sights to aim the boxes just below the target, so the sensors are parallel with the bore line. |
Configurable distance.
Choose from 2, 6, 10, or 15 foot spacing, measured using marks on the cable itself. |
Wide sensing area.
You can fire up to 6 feet over the sensors, and place the front box up to 15 feet in front of the muzzle. |
Manageable wire.
The wire is flexible, tangle resistant, and can be wrapped up in seconds for quick storage. |
Flexible mounting options.
The boxes can be placed on the ground, bolted to a board, mounted on tripods, taped to your rifle case... you get the idea. |
Long lasting battery.
The integrated battery provides over 60 hours on a charge so you'll never have to worry about it dying at the range. |
Shoot first, record later.
500 shots are saved in memory so you can go home and deal with the data in comfort. |
Large display.
The easy to read, back-lit display ensures you can keep testing at sunset. |
Simple remote control.
The RF remote makes reviewing your shots easy and intuitive. No frills, no complications. |
Quality construction.
The cast aluminum boxes are durable and look great. Please don't shoot them! |
Everything in its place.
The soft carrying case has pockets for accessories and protects the boxes in travel. |
Please review the reference manual for a more in-depth look at the features and methods of use.
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How do you approach load development?
As I discuss in my blog, my preferred method of developing a long range load is to treat dispersion and velocity as separate variables to be optimized. At 100 yards, you can shoot groups and measure velocity with no interference from wind, mirage, and other factors. There is absolutely no need to verify at long range.
Where this method falls apart is when your chronograph is not precise enough to be effective. In this chapter from his book, Bryan Litz measured the random error of many popular chronographs (such as the Chrony and Magnetospeed) to be around 3-4 fps SD. In other words, for a 20 shot sample you should expect a random spread up to 16 fps purely generated by the chronograph - as much as the ammo itself should have!
The Two-Box Chrono opens up the possibility for more scientific load development methods.
We measured 1000 test shots and the largest error was 3 fps. The overall error SD was 0.5 fps (0.02%), and 95% of the shots were within 1 fps. We were quite excited (and surprised, to be honest) to achieve this. If you'd like to dig into the raw data for yourself, here's the spreadsheet.
The correct average velocity will be reported if the sensors are aligned properly. The Two-Box Chrono includes markings on the wire for distancing and magnetic sights to help align the sensors below the target, parallel to the bullet path. If the boxes look to be as straight as you can make it, the absolute accuracy of the average should be within 10 fps.
Even if the boxes are not well aligned, the offset is constant. The readings will track correctly with velocity, so there's no need to align it perfectly if repeatability is what matters to you. Just get on with shooting.
The Two-Box Chrono is unique and easy to use once you find a method that works for you. Refer to the manual for more information, and feel free to email me with any questions you may have.
As I discuss in my blog, my preferred method of developing a long range load is to treat dispersion and velocity as separate variables to be optimized. At 100 yards, you can shoot groups and measure velocity with no interference from wind, mirage, and other factors. There is absolutely no need to verify at long range.
Where this method falls apart is when your chronograph is not precise enough to be effective. In this chapter from his book, Bryan Litz measured the random error of many popular chronographs (such as the Chrony and Magnetospeed) to be around 3-4 fps SD. In other words, for a 20 shot sample you should expect a random spread up to 16 fps purely generated by the chronograph - as much as the ammo itself should have!
The Two-Box Chrono opens up the possibility for more scientific load development methods.
We measured 1000 test shots and the largest error was 3 fps. The overall error SD was 0.5 fps (0.02%), and 95% of the shots were within 1 fps. We were quite excited (and surprised, to be honest) to achieve this. If you'd like to dig into the raw data for yourself, here's the spreadsheet.
The correct average velocity will be reported if the sensors are aligned properly. The Two-Box Chrono includes markings on the wire for distancing and magnetic sights to help align the sensors below the target, parallel to the bullet path. If the boxes look to be as straight as you can make it, the absolute accuracy of the average should be within 10 fps.
Even if the boxes are not well aligned, the offset is constant. The readings will track correctly with velocity, so there's no need to align it perfectly if repeatability is what matters to you. Just get on with shooting.
The Two-Box Chrono is unique and easy to use once you find a method that works for you. Refer to the manual for more information, and feel free to email me with any questions you may have.