I've used this a few times in the past, works fine to at least make sure your on paper (and better to within a few clicks if done properly), but had forgotten about it until today when I came across it again in my saved emails while cleaning up. Its actually a combination of three different emails all using the same reference point established in the pocedure outlined below Thought i'd post it as it may help someone.
How to construct and use an improvised reasonably accurate laser bore sight device for 25 meter/300 meter - for 5.56 M-4 platform, may be used with 7.62 with suitable changes, for weapon mounted laser zero using constant offset (not point of impact/point of aim) or an EOTech red dot sight.
Materials needed:
1. One fired 5.56 NATO brass casing (not .223 SAMMI spec brass or steel casing) with no primer, bullet, or powder in place. The casing should be in good condition and not bulged, deformed, dented, creased, or damaged in any manner, normal chambering and ejection markings are ok, the casing should be clean and free of dirt, debris, grim, cleaners, or lubricants. You should be able to see through this casing from end to end without obstruction through the bullet end and the primer end. Its better if the inside of the casing is dull to flat blackened (best). DO NOT USE LIVE AMMO - DO NOT USE A CASING FOR RELOAD WITH AN UNFIRED PRIMER. - to manufacture this casing. The casing should be manufactured from a fired spent casing, when removing the fired primer do not damage the casing or enlarge the primer hole.
2. A spare tubed weapon, or other suitable, laser (see note at bottom).
3. A sheet of white 8 1/2 x 11 (or reasonable size) paper.
4. Scotch tape
5. Pencil
Other:
One assistant is needed.
Procedure:
CAUTION: Ensure no live ammo is present in the work area.
1. Remove the upper portion of the rifle using the take down pins, remove the bolt carrier group and charging handle, and place the rifle upper portion in a solid clamp device so it remains firmly held and stable and is level horizontally and vertically with the front BUIS sight pointing straight up. Ensure any sightable devices to be adjusted (e.g. red dots, weapon laser) have already been placed on the rifle upper portion prior to mounting the rifle upper portion in the holding device. All points are looking from the butt end of the rifle.
2. Point the fixed upper rifle portion at a flat vertical surface 10 meters from the end of the rifle barrel (including flash suppressor - remove sound suppressor if any).
3. Have the assistant attach the sheet of paper to the flat vertical surface using a piece of scotch tape approximately at the level of and in line with the barrel line vertically and horizontally. The paper postion can be verified by visually looking down the barrel towards the vertical surface paper location.
4. Insert the 5.56 brass casing by hand in the chamber up into the barrel end as if it was a round being chambered from a magazine. Ensure the casing is fully inserted and remains so in a stable and firm seating without movement. Do not cant the case in the chamber as it needs to be as straight as possible. Use small pieces of scotch tape opposite each other on the casing if necessary to remove movement.
5. Using the tubed laser held by hand, place the laser aperture at the bolt end of the rifle upper portion where the bolt carrier group is placed in the upper rifle portion so the laser beam shines into the rifle upper portion towards and into the chambered brass casing primer hole.
6. Using small movements, adjust the laser body position by hand (move it around) until the brightest part of the laser dot strikes the paper. When the brightest portion of the laser dot strikes the paper have the assistant use the pencil to mark the center of the laser dot on the paper with a small visible dot. (Note: If the paper is not in the correct postion for the laser dot to strike, adjust the paper position not the rifle upper portion position.)
7. Once satisfied with the marked position on the paper, remove the laser used in this procedure and turn it off, remove the casing used. If conducted properly, without moving the paper or the weapon upper portion, you now have an (reasonably) accurate bore sight reference point for adjusting sighting devices such as weapon mounted laser or EOTech sight. This reference point will remain accurate as long as the rifle upper portion remains in place and is not moved and the paper has not moved after the reference point was marked. As long as these postions of the rifle upper portion and the paper remain un-changed, during this bore sight session, the weapon mounted laser and/or EOTech sight may be "bore sighted" using the reference point.
Note: Cheap lasers will work for this process for the improvised bore sight device if you do not have a quality spare weapon laser available if the cheap laser is of suitable brightness. For a person experienced in this procedure it takes approximately five minutes to accomplish once set up. Refine zero as necessary on firing range using live fire.
Example: Say we had an EOTech 512 (has a 1 MOA dot) mounted on the weapon and we wanted to adjust it for a 300 meter zero and wanted to be pretty close when we got to the range to zero with live fire. Do the above and establish the reference point and adjust the EoTech dot to the center of point shown in the pic below (not to scale - borrowed from an EOTech target for this example, you can get the actual target from the EOTech web site):
Procedure Modification: To modify the procedure for 50 yard/200 meter zero of a laser device for constant offset directly above, below, to the left or right, of and parallel to the rifle bore line center (center of the rifle barrel parallel) and mounted on the hand guard rails (assumes weapon is zero'd using 50 yard/200 meter zero) using :
1. The distance from end of the barrel (including flash suppressor - remove sound supressor if any) to vertical surface with paper is changed from 10 meters to 26 feet 4 inches. All points are looking from the butt end of the rifle.
2. After the reference point is established on the paper from the above procedure (using the chmnaged distance of 26 feet 4 inches), measure, in centimeters, from the center of the laser aperture to the center of the rifle bore (center of the barrel). On the paper mark a spot with this measurement from the reference point in the same orientation the laser is offset. For example, if the laser is mounted below and parallel to the bore center line - and the laser aperture is 5 cm below and parallel to the bore center line, on the paper mark a point that equals this measurement from the reference point in the same orientation as the laser (directly below the reference point by 5 cm for this example). Adjust the weapon laser to this point on the paper.
3. Test fire on the range, the laser point on target should be the distance measured in procedure modification step 2 above from the point of impact +/- approximately 2.75 inches above or below (or left or right), depending on mounting orientation axis of the laser, or less up to 200 meters using M855 NATO rounds. Refine as necessary using live fire such that the laser dot on target at 200 meters is the same distance from point of impact as was measured in procedure modification step 2, within +/- 25% of that measurement for distances between 0 to approximately 180 meters. (this does not include effects of wind on the bullet - its better to mount a laser so the aperture is directly below or above and parallel to the bore line).
4. For the AN/PEQ series (or housing form) types of laser devices, or two axis offset lasers: The device aperture is offset in the X and Y directions. You will need to measure the aperture from bore line measurement in both the X and Y axis for these types of lasers. For example if the aperture is 3 cm above the bore line and 3 cm to the left, on the paper from the reference point you mark a point at 3 cm above and 3 cm to the left of the reference point and adjust the weapon laser to this point.
Using an offset mounted weapon laser and the above procedure, the weapon laser dot will remain a constant known distance from the point of impact out to 200 meters. For example, with a weapon laser dot from a laser mounted under and parallel to the weapon bore line at 5 centimeters you know the round will impact the target 5 centimeters above or below (depending on distance) the laser dot as long as M855 ammo is used. Of course for long distance shots such as greater than 200 meters distance bullet path change from wind may have a greater effect for windage so the shooter may need to compensate for wind. If using a different ammo and/or longer ranges (if the laser dot can be seen at the longer range and can be placed on target), suitable adaptations of the procedure can be made in these particular aspects. This method makes shot placement more predictable then guessing with the more traditional point of impact/point of aim method where the weapon laser is only zeroed at the distance it was zeroed at.
Edit Add: Had a question on this. Yes, the laser beam shines through the end of the 5.56 round casing through the primer hole out where the bullet is normally seated in the case then down the barrel. The case when seated fully and properly will be very close to, or at, the bore center. When a laser dot, and the brightest part of the dot, is seen on the paper it means the laser was lined up with bore center (since the laser beam travels in a straight line). You may get some reflection from inside the bore on chromed barrels show up on the paper, you will know this is different as it will be spread around and not be in a small dot and will appear more diffused. When you have a dot form and its at its brightest thats when and where you mark the reference point on the paper. The movements of the laser to do this can be very small, a slight flex of the hand is all thats needed when you get close, so have a steady hand. This is basically the same thing the bullet case type laser bore sighters use except they have the bolt hold the case like it does a normal round and their laser is built into the case.
How to construct and use an improvised reasonably accurate laser bore sight device for 25 meter/300 meter - for 5.56 M-4 platform, may be used with 7.62 with suitable changes, for weapon mounted laser zero using constant offset (not point of impact/point of aim) or an EOTech red dot sight.
Materials needed:
1. One fired 5.56 NATO brass casing (not .223 SAMMI spec brass or steel casing) with no primer, bullet, or powder in place. The casing should be in good condition and not bulged, deformed, dented, creased, or damaged in any manner, normal chambering and ejection markings are ok, the casing should be clean and free of dirt, debris, grim, cleaners, or lubricants. You should be able to see through this casing from end to end without obstruction through the bullet end and the primer end. Its better if the inside of the casing is dull to flat blackened (best). DO NOT USE LIVE AMMO - DO NOT USE A CASING FOR RELOAD WITH AN UNFIRED PRIMER. - to manufacture this casing. The casing should be manufactured from a fired spent casing, when removing the fired primer do not damage the casing or enlarge the primer hole.
2. A spare tubed weapon, or other suitable, laser (see note at bottom).
3. A sheet of white 8 1/2 x 11 (or reasonable size) paper.
4. Scotch tape
5. Pencil
Other:
One assistant is needed.
Procedure:
CAUTION: Ensure no live ammo is present in the work area.
1. Remove the upper portion of the rifle using the take down pins, remove the bolt carrier group and charging handle, and place the rifle upper portion in a solid clamp device so it remains firmly held and stable and is level horizontally and vertically with the front BUIS sight pointing straight up. Ensure any sightable devices to be adjusted (e.g. red dots, weapon laser) have already been placed on the rifle upper portion prior to mounting the rifle upper portion in the holding device. All points are looking from the butt end of the rifle.
2. Point the fixed upper rifle portion at a flat vertical surface 10 meters from the end of the rifle barrel (including flash suppressor - remove sound suppressor if any).
3. Have the assistant attach the sheet of paper to the flat vertical surface using a piece of scotch tape approximately at the level of and in line with the barrel line vertically and horizontally. The paper postion can be verified by visually looking down the barrel towards the vertical surface paper location.
4. Insert the 5.56 brass casing by hand in the chamber up into the barrel end as if it was a round being chambered from a magazine. Ensure the casing is fully inserted and remains so in a stable and firm seating without movement. Do not cant the case in the chamber as it needs to be as straight as possible. Use small pieces of scotch tape opposite each other on the casing if necessary to remove movement.
5. Using the tubed laser held by hand, place the laser aperture at the bolt end of the rifle upper portion where the bolt carrier group is placed in the upper rifle portion so the laser beam shines into the rifle upper portion towards and into the chambered brass casing primer hole.
6. Using small movements, adjust the laser body position by hand (move it around) until the brightest part of the laser dot strikes the paper. When the brightest portion of the laser dot strikes the paper have the assistant use the pencil to mark the center of the laser dot on the paper with a small visible dot. (Note: If the paper is not in the correct postion for the laser dot to strike, adjust the paper position not the rifle upper portion position.)
7. Once satisfied with the marked position on the paper, remove the laser used in this procedure and turn it off, remove the casing used. If conducted properly, without moving the paper or the weapon upper portion, you now have an (reasonably) accurate bore sight reference point for adjusting sighting devices such as weapon mounted laser or EOTech sight. This reference point will remain accurate as long as the rifle upper portion remains in place and is not moved and the paper has not moved after the reference point was marked. As long as these postions of the rifle upper portion and the paper remain un-changed, during this bore sight session, the weapon mounted laser and/or EOTech sight may be "bore sighted" using the reference point.
Note: Cheap lasers will work for this process for the improvised bore sight device if you do not have a quality spare weapon laser available if the cheap laser is of suitable brightness. For a person experienced in this procedure it takes approximately five minutes to accomplish once set up. Refine zero as necessary on firing range using live fire.
Example: Say we had an EOTech 512 (has a 1 MOA dot) mounted on the weapon and we wanted to adjust it for a 300 meter zero and wanted to be pretty close when we got to the range to zero with live fire. Do the above and establish the reference point and adjust the EoTech dot to the center of point shown in the pic below (not to scale - borrowed from an EOTech target for this example, you can get the actual target from the EOTech web site):
Procedure Modification: To modify the procedure for 50 yard/200 meter zero of a laser device for constant offset directly above, below, to the left or right, of and parallel to the rifle bore line center (center of the rifle barrel parallel) and mounted on the hand guard rails (assumes weapon is zero'd using 50 yard/200 meter zero) using :
1. The distance from end of the barrel (including flash suppressor - remove sound supressor if any) to vertical surface with paper is changed from 10 meters to 26 feet 4 inches. All points are looking from the butt end of the rifle.
2. After the reference point is established on the paper from the above procedure (using the chmnaged distance of 26 feet 4 inches), measure, in centimeters, from the center of the laser aperture to the center of the rifle bore (center of the barrel). On the paper mark a spot with this measurement from the reference point in the same orientation the laser is offset. For example, if the laser is mounted below and parallel to the bore center line - and the laser aperture is 5 cm below and parallel to the bore center line, on the paper mark a point that equals this measurement from the reference point in the same orientation as the laser (directly below the reference point by 5 cm for this example). Adjust the weapon laser to this point on the paper.
3. Test fire on the range, the laser point on target should be the distance measured in procedure modification step 2 above from the point of impact +/- approximately 2.75 inches above or below (or left or right), depending on mounting orientation axis of the laser, or less up to 200 meters using M855 NATO rounds. Refine as necessary using live fire such that the laser dot on target at 200 meters is the same distance from point of impact as was measured in procedure modification step 2, within +/- 25% of that measurement for distances between 0 to approximately 180 meters. (this does not include effects of wind on the bullet - its better to mount a laser so the aperture is directly below or above and parallel to the bore line).
4. For the AN/PEQ series (or housing form) types of laser devices, or two axis offset lasers: The device aperture is offset in the X and Y directions. You will need to measure the aperture from bore line measurement in both the X and Y axis for these types of lasers. For example if the aperture is 3 cm above the bore line and 3 cm to the left, on the paper from the reference point you mark a point at 3 cm above and 3 cm to the left of the reference point and adjust the weapon laser to this point.
Using an offset mounted weapon laser and the above procedure, the weapon laser dot will remain a constant known distance from the point of impact out to 200 meters. For example, with a weapon laser dot from a laser mounted under and parallel to the weapon bore line at 5 centimeters you know the round will impact the target 5 centimeters above or below (depending on distance) the laser dot as long as M855 ammo is used. Of course for long distance shots such as greater than 200 meters distance bullet path change from wind may have a greater effect for windage so the shooter may need to compensate for wind. If using a different ammo and/or longer ranges (if the laser dot can be seen at the longer range and can be placed on target), suitable adaptations of the procedure can be made in these particular aspects. This method makes shot placement more predictable then guessing with the more traditional point of impact/point of aim method where the weapon laser is only zeroed at the distance it was zeroed at.
Edit Add: Had a question on this. Yes, the laser beam shines through the end of the 5.56 round casing through the primer hole out where the bullet is normally seated in the case then down the barrel. The case when seated fully and properly will be very close to, or at, the bore center. When a laser dot, and the brightest part of the dot, is seen on the paper it means the laser was lined up with bore center (since the laser beam travels in a straight line). You may get some reflection from inside the bore on chromed barrels show up on the paper, you will know this is different as it will be spread around and not be in a small dot and will appear more diffused. When you have a dot form and its at its brightest thats when and where you mark the reference point on the paper. The movements of the laser to do this can be very small, a slight flex of the hand is all thats needed when you get close, so have a steady hand. This is basically the same thing the bullet case type laser bore sighters use except they have the bolt hold the case like it does a normal round and their laser is built into the case.
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