Nota Bene: this post contains excerpts from the Labradar user manual and quick start guide available at the official site here: https://mylabradar.com/download/. These, contrary to most of the rest of this site, are certainly not under WTFPL; I hope Labradar would not mind me repeating their instructions.
1. Read the Labradar manual, at least the quick setup guide. There are pictures! All the recommendations are there for a reason, specifically…
2. Make sure the device is pointed to the target you are shooting at. The closer the bullet is to the axis of the beam — the more reliable are the measurements.
3. Respect the distance from the muzzle to the radar. If the settings say “30 cm muzzle offset”, make sure your muzzle is 25-30 cm away from the radar. If you place your muzzle 1 m away, it would probably still record, but the readings would have a significant error. The reason for this is simple: Labradar can only mesure the radial velocity from the radar, which is not exactly the same as the actual bullet velocity, because the axis of the radar beam does not coincide with trajectory. It is, however, possible to calculate the real projectile speed (and that’s what the device does and displays), but to be accurate it need to know the exact distance from the muzzle.
4. Make sure your tripod is very solid, and very well grounded. Do not hesitate to load the mounting platform with weights. Reason: if Labradar moves during the measures, the results can be completely random.
5. If you have a well-developed… muzzle brake — protect your investment, shield Labradar from the muzzle blast with, e.g., a wooden plank or a crate of ammo. Reason: same as (4) — even if the device casing is made from impact-resistant plastic, it can still shake under the blast wave = move = mess up the measurements.
6. Make sure your range is free of obstacles: ideally this should be an open field; there should be no high bumps on the ground within the radar range. The trajectory should be clear from all obstacles 5 m left, right and up. Reason: signal reflections, which can cause radar noise and significantly decrease the accuracy of measurements.
7. Do not use steel targets, if these are within the radar’s range (< 200 m). Use only wood, cardboard or paper. Reason: reflections; a small metal bullet on the background of a big metal target would be very hard for the equipment to detect and trace.
And specifically for BC measurements with Labrabaco:
8. Configure your maximum display distance at 200 m or 200 yd. The track will not register that far, but it will tell Labradar to try recording as far as the signal goes. The longer the track — the better the data.