I am the team "armorer" for a US college pistol team, and I'm learning how to repair competition 10 meter air pistols. An important part of the process is measuring & adjusting velocities. In the past, I have used Combros, which are spec'd to be 1% accuracy. I have two at home, and we have one at the college. I haven't managed to shoot one yet, but it would certainly be easy to do. I recently picked up one of the Chinese HT-X3006 units, which claims 0.5% accuracy. I've 3D printed a bunch of adapters so I can easily pop it onto a variety of pistols.
https://www.thingiverse.com/thing:6977381
It's easier to use than the Combros, and the mounts I designed make it pretty idiot proof in terms of not shooting the sensors.
I tested the HT-X3006 on a Benelli Kite I had just rebuilt. If they are up to factory spec, the velocity shouldn't vary by more than +/- 1 meter/sec. I was seeing variations of up to twice that. I didn't know if it was the pistol, or the Chinese chrono. I tested the pistol with all three Combros, firing 25 shot strings with each. Nothing matched up very well:
The Combros are roughly within 1% of each other, but the "more accurate" HT-X3006 is a couple percent above ALL of the Combros. The standard deviation numbers are all big enough that I think the pistol has a problem. The catch is that I have no idea which chronograph to use to test it when I try to fix it.
I also own a LabRadar V1 Doppler radar chronograph, which is supposed to be good to 0.1%. The little chronos are WAY easier to use, so I figured I could set up the LabRadar and use it to come up with calibration/correction formulas for the others. I could shot through the small chronos, and use the radar to measure each shot at the same time, which should give me really good data. Or so I thought...
I set up the LabRadar in my basement shop, and spent several hours trying to get ONE valid reading. In order to get 10 meters, I have to shoot though a doorway, and the place is very cluttered. After playing with all sorts of settings, I concluded that I was getting too many reflections off of various surfaces, and/or the distance was too short.
Today, I dragged the LabRadar and the HT-X3006 into the school 50 foot range, which is relatively open. I could immediately get velocity readings, and I tried to get some comparison data between the two. I need to plot all the data, but here are a few samples (all in fps):
The LabRadar varied all the way from 389 to 477 fps (an 88 fps spread). The HT-X3006 was considerably more consistent, going from 441 to 480.8 fps (39.8 fps spread). The "match" between velocities on the SAME shot was universally horrible.
I understand the "physics" of the HT-X3006, and it's pretty basic. There's only so much that can go wrong. I also used to work as a microwave engineer, and Doppler radar is pretty well established technology, but picking up a tiny pellet seems to be a problem. I now have FIVE chronographs, and I can't trust ANY of them. At this point, the $25 Chinese box is giving me much more believable data than the filthy expensive 0.1% accuracy radar.
Given that they are cheap, I may just get several of the HT-X3006's and see how they compare. I can get four for what I paid for one Combro. I don't actually need to know the absolute velocity super accurately, but I need to be able to measure the consistency to at least 1 fps or better.
I took a look at the Garmin Xero C1, and it claims slightly better than 1% accuracy, but there's no info on how repeatable they are. I also have no idea it it would work in my shop at home. The convenience of the Combros and the HT-X3006 is hard to beat. I've measured a number of air pistols that fire consistently around +/- 1 fps with Combros in the past, so they appear to be pretty repeatable, even if the absolute velocity is slightly suspect.
I could get a larger conventional chronograph, but I really don't have a good place to set one up at home. I even have an old Oehler 35P with three sensors, but that's WAY to big to set up in my shop.
So, now that you've suffered through my tales of woe, does anyone have suggestions for a chrono I can actually trust? I'd blow the big bucks on a Garmin if I KNEW it would work well with pellets, especially if I could use it at home. Based on my experience with the LabRadar, I don't trust a Doppler system in that environment, which leaves me with optical time & distance gadgets.
Thanks!
https://www.thingiverse.com/thing:6977381
It's easier to use than the Combros, and the mounts I designed make it pretty idiot proof in terms of not shooting the sensors.
I tested the HT-X3006 on a Benelli Kite I had just rebuilt. If they are up to factory spec, the velocity shouldn't vary by more than +/- 1 meter/sec. I was seeing variations of up to twice that. I didn't know if it was the pistol, or the Chinese chrono. I tested the pistol with all three Combros, firing 25 shot strings with each. Nothing matched up very well:
| Chronograph | Ave. Velocity | Standard Dev. |
| HT-X3006 | 138.04 m/sec | 1.668 m/sec |
| Combro #1 | 133.60 m/sec | 1.433 m/sec |
| Combro #2 | 134.30 m/sec | 1.300 m/sec |
| School Combro | 135.10 m/sec | 1.758 m/sec |
The Combros are roughly within 1% of each other, but the "more accurate" HT-X3006 is a couple percent above ALL of the Combros. The standard deviation numbers are all big enough that I think the pistol has a problem. The catch is that I have no idea which chronograph to use to test it when I try to fix it.
I also own a LabRadar V1 Doppler radar chronograph, which is supposed to be good to 0.1%. The little chronos are WAY easier to use, so I figured I could set up the LabRadar and use it to come up with calibration/correction formulas for the others. I could shot through the small chronos, and use the radar to measure each shot at the same time, which should give me really good data. Or so I thought...
I set up the LabRadar in my basement shop, and spent several hours trying to get ONE valid reading. In order to get 10 meters, I have to shoot though a doorway, and the place is very cluttered. After playing with all sorts of settings, I concluded that I was getting too many reflections off of various surfaces, and/or the distance was too short.
Today, I dragged the LabRadar and the HT-X3006 into the school 50 foot range, which is relatively open. I could immediately get velocity readings, and I tried to get some comparison data between the two. I need to plot all the data, but here are a few samples (all in fps):
| Test | LabRadar | HT-X3006 |
| 1 | 463 | 480.8 |
| 2 | 389 | 444.1 |
| 3 | 417 | 443.1 |
| 4 | 406 | 461.1 |
The LabRadar varied all the way from 389 to 477 fps (an 88 fps spread). The HT-X3006 was considerably more consistent, going from 441 to 480.8 fps (39.8 fps spread). The "match" between velocities on the SAME shot was universally horrible.
I understand the "physics" of the HT-X3006, and it's pretty basic. There's only so much that can go wrong. I also used to work as a microwave engineer, and Doppler radar is pretty well established technology, but picking up a tiny pellet seems to be a problem. I now have FIVE chronographs, and I can't trust ANY of them. At this point, the $25 Chinese box is giving me much more believable data than the filthy expensive 0.1% accuracy radar.
Given that they are cheap, I may just get several of the HT-X3006's and see how they compare. I can get four for what I paid for one Combro. I don't actually need to know the absolute velocity super accurately, but I need to be able to measure the consistency to at least 1 fps or better.
I took a look at the Garmin Xero C1, and it claims slightly better than 1% accuracy, but there's no info on how repeatable they are. I also have no idea it it would work in my shop at home. The convenience of the Combros and the HT-X3006 is hard to beat. I've measured a number of air pistols that fire consistently around +/- 1 fps with Combros in the past, so they appear to be pretty repeatable, even if the absolute velocity is slightly suspect.
I could get a larger conventional chronograph, but I really don't have a good place to set one up at home. I even have an old Oehler 35P with three sensors, but that's WAY to big to set up in my shop.
So, now that you've suffered through my tales of woe, does anyone have suggestions for a chrono I can actually trust? I'd blow the big bucks on a Garmin if I KNEW it would work well with pellets, especially if I could use it at home. Based on my experience with the LabRadar, I don't trust a Doppler system in that environment, which leaves me with optical time & distance gadgets.
Thanks!
