Chronograph comparison, Garmin, LabRadar, Shooting Chrony

[vaguru]

Yesterday I had the opportunity to chrono the same ammo over 3 different chronos at the same time. They were a Garmin, a LabRadar and an old Shooting Chrony optical. The Chrony was set 5' from the muzzle while the other 2 were on the bench.

The rifle was a 22LR shooting a known lot of good ammo. The LabRadar and the Chrony recorded virtually the same FPS, only differing by 2 FPS. The Garmin was very different in this regard recording 50 FPS lower. velocity. The ES was was basically the same for all the units, varying only 1 FPS, 12 to 11 FPS.

Any idea as to what is going on with the discrepancy with the reading on the Garmin?

 

[walterg]

I have compared my Labradar to my Garmin side by side and the velocities they registered were basically the same. The only difference is the Garmin displays velocities to the tenth and Labradar doesn't display decimals.

Make sure the settings in the Garmin and Labradar match how you have them setup in relation to the muzzle.

 

[bulletbluesky]

Maybe alignment issues (make sure it's not angled wrt bore direction and that bullet can travel at least 20 yards to target without obstructions in a way). If not, than must be gremlins/aliens issues

 

[Defender32]

1 other thing to check is make sure the Garmin has the correct bullet weight set in it.

I have dont this similar test with Garmin, FX Radar, FX True Ballistics and Magnetospeed. all of them were within 2-3 FPS and 1 on ES & SD. Who knows which one is right????? Trust the one you ate using for your gathering just like you do your Range Finder for yardage.

 

[DFOOSKING]

How about you run the data on your solver using the two different velocities and see which gives closer solutions and let that be what we value. Then value that tool over the other regardless if the speed seems wrong. At least till better comes along.

Surely the paper targets will tell you more whether the ammo is worth using.... than the chronograph alone.

 

[Baron23]

1 other thing to check is make sure the Garmin has the correct bullet weight set in it.

Why?

 

[Defender32]

Why?

Because it's a setup option it COULD make a difference. I don't know that it will. I know that Garmin didn't put it in there for shits and giggles. I set it for every bullet weight I'm shooting.

Bad info in means BAD info out. Dont do it if you're not going to do it right.

 

[Baron23]

Because it's a setup option it COULD make a difference. I don't know that it will. I know that Garmin didn't put it in there for shits and giggles. I set it for every bullet weight I'm shooting.

Bad info in means BAD info out. Dont do it if you're not going to do it right.

As far as I am aware, bullet weight is generally only applicable to determining power factor (energy down range).

From Garmin's owner's manual.

Since the Garmin doesn't provide downrange velocities (as the LabRadar does somewhat well), I don't see the utility of this.

Thanks for the reply.

 

[6.5SH]

Yesterday I had the opportunity to chrono the same ammo over 3 different chronos at the same time. They were a Garmin, a LabRadar and an old Shooting Chrony optical. The Chrony was set 5' from the muzzle while the other 2 were on the bench.

The rifle was a 22LR shooting a known lot of good ammo. The LabRadar and the Chrony recorded virtually the same FPS, only differing by 2 FPS. The Garmin was very different in this regard recording 50 FPS lower. velocity. The ES was was basically the same for all the units, varying only 1 FPS, 12 to 11 FPS.

Any idea as to what is going on with the discrepancy with the reading on the Garmin?

Re-do the test without the Chrony downrange. Downrange clutter = bad.

 

[Rocketvapor]

Both of the radar units are 24GHZ. Was there beam interference?

Thanks

 

[bulletbluesky]

Both of the radar units are 2.4GHZ. Was there beam interference?

You meant 24 GHz. Interference of this kind would probably result in "no-read" error

 

[vaguru]

Re-do the test without the Chrony downrange. Downrange clutter = bad.

Did that. Removed Chrony and Garmin still read exactly the same as with it set up. Don't understand the 50 fps difference.

 

[vaguru]

How about you run the data on your solver using the two different velocities and see which gives closer solutions and let that be what we value. Then value that tool over the other regardless if the speed seems wrong. At least till better comes along.

Surely the paper targets will tell you more whether the ammo is worth using.... than the chronograph alone.

Ran fps and BC for both velocities through Chairgun ellite. The higher velocity shown by the Chrony and the LabRadar hit spot on at 100 yds. The results from the Garmin required 2 more clicks (.2 mils) at 100 and hit high by that amount.

 

[Potsy]

Definitely weird.
Ran 1 round out of my .22 BR the other day over my Pro-Chrono to get a ladder started. 2814fps.
Shot the ladder next to a friend’s Garmin, 2799fps at the same charge weight. Given it was 7 degrees cooler with the Garmin, plus velocity variation at that charge weight, I felt like it was close enough.
For a statistical sample of one……FWIW….

 

[grauhanen]

Not all chronographs -- certainly the more affordable optical ones -- are equal. Perhaps this includes some such as this particular Garmin, despite its use of doppler radar. It's not as though the Garmin is a "high priced" device.

 

[6.5SH]

Did that. Removed Chrony and Garmin still read exactly the same as with it set up. Don't understand the 50 fps difference.

I vaguely recall someone else mentioning being 50 fps off in one of the other giant threads. I wonder if it is a similar to the issue with some ProChrono being exactly 75 fps slow (which I assume is some calibration issue from the factory).

I'd try again and pay attention to the positioning of the unit; bipod/rest not in the way, offset per the manual, nothing downrange etc.
Then switch the LabRadar off and see if the Xero speeds up. If it does then is an interference issue.

If issue persists I'd try it again with a different gun/cartridge and see if the same pattern exists. If so, I'd be contacting Garmin with the findings.

 

[secondofangle2]