What is a Bore Sight Offset?

For Walkthrough Wednesday, we are continuing our discussion on how to zero the M4A1 Carbine and coach our Paratroopers through the zero process. Specifically, we will be addressing how to boresight. The reference for this discussion is appendix E, TC 3-22.9, Change 2, dated August 2017 and TM 9-5860-226-13&P, dated May 2013.

As a refresher, the borelight is an eye-safe laser that is used to boresight optics, iron sights, and aiming lasers. The borelight assists the first shot group hitting the 25-m zeroing target …
This picture illustrates the 10-meter offset for the M68 CCO. You must make sure that you have the right ‘Recipe for Success’ by verifying the offset is the correct one for your Weapon/ Optic Combination IN the offset package the Master Gunner Cell has Put together, you can find that information at the top of the offset.

Once that is complete, you move on to live fire confirmation. The picture on the right illustrates what the offset looks like for top mounted PEQ-15 at 25 meters. Keep in mind, your POA is still center mass, the rounds are striking inside the POI, which is 2.2 centimeters left and 1.9 centimeters up.

The similarities between the 10 and 25 meter offsets are: they zero the weapon and sight combination for 300M, 400M, or 500M (Depending on weapon system). And they are specific to weapon and sight configurations. (Need to have the appropriate offset). The differences between the ten and 25 meter offsets are: 25M offsets must be used on a 25 meter zero range with live ammunition (the only exception being Machine guns which are zeroed at 10 meters), and you must prepare the 25M zero target to zero infrared aiming lasers.

GENERIC 10M BORESIGHT TARGET:

Since the offset on a 10M Boresight Target is a mathematical calculation with symbols placed on predetermined grid coordinates on a sheet of paper with a 1 cm grid pattern, a soldier can create a 10M Boresight Target as long as the grid coordinates are known for the aiming device being mounted to what weapon and in what location it will be mounted on the weapon. This keeps the amount of 10M Boresight Targets needed to a minimum.

In order to create a 10M Boresight Target the soldier must:

• Find the grid coordinates for the specific weapon/ sight configuration which can be found on the pre-made 10M Boresight Target.

• Count the number of squares starting from center of the bore light circle on the offset to the desired point of aim. Each template also provides you with a number formula for the proper offset. Example (L2.0, U2.4): Starting from the center of the bore light circle (0.0, 0.0) move LEFT 2 squares and UP 2.4 squares.

• Once the center of the point of aim for the aiming device is found, draw in the appropriate symbol.

The 10M Boresight Target is complete and ready to be used

The different symbols represent on the 10M Boresight Target: The circle cross hair represents the where to aim the optic or laser, the gray circle represents where the borelight laser must be placed, And The circle cross hair with the gray ovals on the side represents where to aim the reticle of the AN/ PAS-13 Thermal Weapon Sight.

So to sum up, we’ve discussed what we zero and boresight at ten and twenty five meters. Leaders of all levels need to educate themselves now on this so that they can be more efficient in their use of one of our most valuable assets: range time. Next week, we will continue our discussion as we address how to zero the boresight.

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