This post is not going to cover all the things we do at chrono, because I like to keep these blog posts short and to the point. But I want to explain, to competitors, about the process used at chronograph to determine power factor. Why? Because if everything goes normally, the competitor doesn’t have to answer any questions. If things don’t go well, the competitor will have to decide whether to have that last round fired or weighed. Let’s learn why!
The whole chronograph process is covered in Appendix C2 of the rulebook, but the part we are focusing on is covered in items 33-43, in case you want to go read all the details later. We determine power factor by measuring the velocity and weight of the bullets. Most matches ask you to give them 8 rounds in a plastic bag on the first day of the match. This is your sample to be tested at chrono. Alternatively, some matches collect ammo directly from your mags when you come to the chrono stage. That is also acceptable. In either case, one round of ammunition is taken apart and the bullet is weighed. That weight is entered into PractiScore.
When you arrive at chrono, and when the chrono officer tells you to, you will set your firearm on the table. Do not touch it again until instructed to do so. The chrono officer will then do all the equipment checks needed for your division (a topic for another post) and will load three rounds of the ammo you provided into a magazine and fire those rounds over the chronograph and call out the velocities (in feet per second) to an assistant who enters them into PractiScore.
PractiScore will multiply the bullet weight by the average velocity of the three measurements and divide that result by 1000. The resulting number is the power factor for your ammo. If you have declared minor PF, the value needs to be above 125. If you have declared major PF, the number needs to be above 165. PractiScore will show the PF and whether it meets the declared power factor. If you pass, they will ask for you to approve the results and you can retrieve your firearm, when instructed, and go on your way.
But what if you do not meet your declared PF? Don’t panic…yet. You have provided 8 rounds to chrono and at this point they have used 4 of those rounds. They will continue to measure bullet velocities with three more of the rounds. As each additional velocity is entered into PractiScore, the program automatically uses the average of the three highest velocities to recalculate the PF. If your calculated PF now meets your declared PF, you are good to go. If not, there is one last round of ammunition to be tested and you get the choice of measuring the velocity or the weight. If the bullet weight they have measured is what you expect, I would choose to fire it. If the bullet weight they have is lighter than expected, I would probably weigh the bullet and hope it gives a heavier reading.
If the PF is still too low after testing 8 rounds, then if you have declared major PF, and your ammo is only measured to be minor PF, your scores will be recalculated using minor PF. If you have declared minor PF and the ammo is measured as sub-minor, then you can keep shooting the match, but for no score.
Take home lessons: 1.) If you don’t make your declared PF with the first 4 rounds, and they don’t test the other 4 rounds, speak up! 2.) It is not fun when you don’t make PF at a match, so I highly recommend testing your ammo before you go. Anyone that loads their own ammo, most likely has a chronograph. And if you ask nicely, they would probably would let you use it after a local match to test your ammo. It only takes a few minutes and can save your match!