Thank you for joining us with our second issue of “Tech Talk.” In our last issue we talked about setting up your loads for optimum accuracy. Starting with this issue, we will start highlighting the various tools that are used to accomplish these goals. We will start by discussing how we would use the chronograph. Many reloaders are not aware of the usefulness of the chronograph and how to use the information that it gives them during their load development. Some folks will say a chronograph is outside of their budget. However, technology has brought us basic units that come in around $100 and go up from there, depending on the features that you might like.
We will be looking at some of the simple things that you can do to get the most out of your chronograph.
1. Make sure that you are using a fresh alkaline battery, or other good power source. Chronographs are sensitive to voltage drops. This can, and will, affect the readings you will see.
2. Make sure that the sensors are being held as straight and as rigidly as possible. If your unit uses light sensors, make sure that you have as even of a light source as possible.
3. Make sure that when you do your setup that your bullet flight path is parallel with the sensors.
4. Make sure that your unit is placed so that muzzle blast will not knock your unit or sensors over when you fire your rounds. Also, make sure that you align the unit so that the bullet does not make physical contact with any part of the chronograph, or sensors. A lot of good sensors and chronographs have met their doom because of being hit!
When we are using the chronograph to assist in load development, the figure that we need to pay attention to is the SD, the standard of deviation. This is what tells us how far off of the average velocity the average shot is. Generally, the smaller this number, the better. Once we have a safe load established, with the lowest SD, you can start your bullet seating depth tests.
For more detailed information on the various chronograph units and how to best use them, see Bryan Litz’s new book “Modern Advancements In Long Range Shooting, Volume 1.” You will find a large amount of very useful information on this subject in Chapter 15, “Measuring Muzzle Velocity.” Have a great time out at the range!
The array of chronographs as tested. In order from left from right: MagnetoSpeed (not visible), indoor Oehler on 12 foot rail, 4 foot Oehler built into light box, two PVM-21’s, Pact, Shooting Chrony, CED-M2, Oehler on a 4 foot rail in natural light, SuperChrony (not shown).