Precision Cut ArcheryPrecision Cut Archery
Precision Cut ArcheryPrecision Cut Archery

Founded in 2023, Precision Cut Archery exists to empower archers to seize those rare, life-defining moments with a cold, calculated confidence.

Documentation

Downrange Speed Sight-In Method

This document details the Downrange Speed sight-in method. This method is extremely precise and is not reliant on accurate user-supplied sight marks.

Which chronograph should I choose?

For a general overview of chronograph types and recommendations, see our comprehensive chronograph guide. Below are specifics for the Downrange Speed method.

The Lab Radar is quicker for this purpose specifically, as it can gather speeds at multiple distances in one shot. It's also quite a bit less expensive than the Garmin Xero.

However, it's bulky, the interface and app is a bit clunky, and it requires an external trigger clamped to your bow to consistently pick up shots in our experience.

The Garmin Xero is much smaller and user friendly. However, it does require that you place it downrange to shoot over the top of it. This can be a bit of a pain if going through this process a lot. Not to mention, somewhat risky to fling arrows over the top of your expensive chronograph. We always recommend putting a target or some other kind of 'shield' in front of the chronograph to protect it from errant shots.

BowBars Archery LLC has made some great 'shields' for the Garmin Xero that are available here. These mount to any tripod, are built out of 1/4" steel, and have a QD system for the Garmin Xero. We highly recommend these if you're going to be using the Garmin Xero for this purpose.

The Data We Need

Density Altitude

Read more about density altitude here.

Ranges

These are the ranges you will measure arrow speeds at.

With the Lab Radar, we like using 20-65 yard readings.

With the Garmin Xero, we like using 1 and 60 yard readings.

The exact choice of ranges hasn't seemed to make any difference in the tapes produced - even in tapes out to 150+ yards. They're all virtually identical.

We choose these ranges for each unit simply for convenience.

Downrange Speeds

These are simply the speeds of your arrow at the ranges specified above.

Reference Mark (optional)

If you are shooting a 'target sight' that has a built in reference scale / click system, you can choose to enter a reference mark for a distance of your choosing. You can think of this like a 'zero' that we use to calculate marks for other distances. This shot-in reference mark should be at a reasonably far distance to minimize error.

Tips for Gathering Downrange Speed Data

Lab Radar Tips

The Lab Radar makes this process very quick and easy, as it gathers speeds at multiple distances in one shot.

Important Lab Radar Settings

These are the most important settings we use for the Lab Radar. Other settings can be set to your preference, but these are the most important for getting consistent and accurate readings with archery equipment.

  • Trigger Source
    • Trigger - Select this if you are using an external trigger such as the JKL Gen 2. We've had much more consistent success using an external trigger over Doppler trigger source.
    • Doppler - Use this if you are using Lab Radar without an external trigger. Some users have reported success with this, but we've had much more consistent success using an external trigger. It can definitely work in a pinch.
  • Velocity Range: Archery
  • TX Power: Standard
  • Trigger Sensitivity: Play around with this. You want it not so sensitive that it triggers when you draw, but you want it to trigger when you shoot.
  • Projectile Offset: This is how far you are to the side of the unit. If you set this to 6 inches, you'll want to position the bow 6 inches from the side of the unit while shooting.
  • Distances: We generally use 20yd and 65yd. 65yd seems to be about the maximum distance that we can consistently get readings at.
  • Arm Time: We prefer to max this out.
  • Screensaver: We prefer to max this out.

Lab Radar Setup

  • We mount the Lab Radar to a tripod.
  • We use an external battery pack (like an Anker battery) to power the Lab Radar. We have not had good luck powering it from AA batteries.
  • We mount the external trigger (JKL Gen 2 or Lab Radar Archery Trigger) to a spring clamp with 3M Dual Lock fastener, hook and loop fastener, or zip ties.

JKL Gen 2 Trigger

Lab Radar Archery Trigger (discontinued)

Other Lab Radar Tips

  • Ensure the Lab Radar is aligned with the target using the sighting groove on the top of the unit. If not aligned, the speed readings can be off.
  • We'll typically shoot at a 70 yard target when getting readings out to 65 yards.
  • The Lab Radar does not pick up the arrow until around 15-20 yards. As such, ensure you have plenty of space between the archer and the target.
  • To test your external trigger, you can arm the unit and tap on the trigger with your finger. You should see the orange light flash and a 'cannot track projectile' message. If you do not see this, your trigger might not be working properly.

Garmin Xero Tips

Gathering downrange speed data with the Garmin Xero is a bit more involved, as it requires you to place it downrange to shoot over the top of it.

Important Garmin Xero Settings

  • Start a new archery session.

  • Projectile weight is optional - use this if you'd like the unit to calculate your KE. It is not required for accurate speed readings.

  • Under Settings > Pro Settings, there is a "Downrange mode" setting you can turn on to enable a visual alert (flashing screen) when a shot is detected. This is helpful to determine if a shot was detected when the unit is placed downrange.

Garmin Xero Setup

  • We mount the Garmin Xero to a tripod.
  • We use a 'shield' to protect the unit from errant shots.
  • The arrow should pass within 5-15 inches of the unit.
  • While gathering velocity readings with the Garmin, leave ~10 yards or so between the unit and the target so the unit has time to detect the arrow.
  • Start by getting your bow on target at 70 yards.
  • Gather a 1 yard velocity reading.
    • At this point, you have your "launch speed" for your setup.
    • Use this to add a "Quick Start" sight in for your setup in our application.
    • We'll use this to determine the ideal positioning of the Garmin at 60 yards.
  • Navigate to the Shot Solver feature of the application and run a simulated 70 yard shot. You can then look at the trajectory plot for this shot.
    • This will give you a good idea of where your arrow is at 60 yards when shooting at a 70 yard target.
    • For example, for this setup, we can see the arrow is about 14 inches from the line of sight at 60 yards, while shooting at a 70 yard target.
  • So, to gather our 60 yard reading, we will want to place the Garmin right in our line of sight, if not a bit higher, to put the unit within the recommended 5-15 inches from the arrow.

Entering the Data

Here's what it looks like to configure a setup with the Downrange Speed sight-in method:

Validating the Sight-In

Once you've entered your data, the easiest way to validate is to print out a sight tape or mark sheet and shoot it in at the range.