Editing Gun Properties on a Foretrex 701

To edit the gun properties on a Foretrex® 701 wrist-mounted navigator follow the steps below.

Edit Applied Ballistics Page Values

1. From the Applied Ballistics page on the Foretrex 701 navigator, select Enter > Profile > Gun Properties.
2. Using the up and down buttons scroll through each field and select Enter to edit values.
3. Select the option you want to edit (input fields):
   • MUZZLE VELOCITY - the speed of the bullet as it leaves the muzzle.
   • ZERO RANGE - the range at which the rifle was zeroed.
   • SIGHT HEIGHT - the distance from the center axis of the rifle barrel to the center axis of the scope.
   • ZERO OFFSET - an optional modification to impact windage at zero range. This is often used when adding a suppressor or using a subsonic load.
     • For example, if you add a suppressor and your bullet impacts the target 1 inch to the left of the expected impact, your ZERO OFFSET is -1 inch. You want to remember to set this to zero when you remove the suppressor.
   • SSF - Elevation - a linear multiplier that accounts for vertical scaling. Not all rifle scopes track perfectly, so the ballistics solution requires a correction to scale according to a particular rifle scope.
     • For example, if a turret is moved 10 mil but the impact is 9 mil, the sight scale is 0.9.
   • SSF - Windage - a linear multiplier that accounts for horizontal scaling. Not all rifle scopes track perfectly, so the ballistics solution requires a correction to scale according to a particular scope.
     • For example, if a turret is moved 10 mil but the impact is 9 mil, the sight scale is 0.9.
   • Twist Rate - the distance it takes for the rifling of your barrel to make one full rotation. Rifle twist is often provided by the gun or barrel manufacturer.

Calibrate Muzzle Velocity

Calibrating the muzzle velocity provides a more accurate solution in the supersonic range for your specific firearm.

1. From the Applied Ballistics page, press ENTER.
2. Select PROFILE > GUN PROPERTIES > CALIBRATE MUZZLE VELOCITY.
3. Select an option:
   • Select RANGE to edit the range - the distance from the muzzle to the target.
   • Select ENTER TRUE DROP to edit the drop distance - the actual distance the bullet falls while in flight to the target, displayed in milliradians (mil) or minute of angle (MOA).
4. Select USE.

TIP: You should enter a value as close as possible to the range suggested in the shooting solution. This is the range where the bullet slows to Mach 1.2 and begins to enter the transonic range.

Calibrate Drop Scale Factor

Garmin recommends you calibrate the muzzle velocity prior to the drop scale factor.

Calibrating the drop scale factor provides a more accurate solution at or beyond the transonic range for your specific firearm.

1. From the Applied Ballistics page, press ENTER.
2. Select PROFILE > GUN PROPERTIES > CALIBRATE DSF.
3. Select an option:
   • Select RANGE to edit the range - the range from which you are shooting. 
   • Select ENTER TRUE DROP to edit the drop distance - the actual distance the bullet falls when fired at a specific range, displayed in milliradians (mil) or minute of angle (MOA).
4. Select USE.

TIP: This range should be within 90% of the recommended range suggested in the shooting solution. Values that are less than 80% of the recommended range will not provide a valid adjustment.

Other Features

Other features of Gun Properties are:

• Select the VIEW DSF TABLE to review the drop scale factor table based on Mach speeds and calibrated drop scale factor values.
• Select the MV-TEMP TABLE to review muzzle velocity adjustments based on ambient temperature.

Helpful Links

• Practical Ballistics
• Ballistic Calibration