A sniper weapon system is a precision instrument. The basic components of a sniper weapon system is the rifle and the optic. This article will not discuss the procedures to fire a rifle, or the fundamentals of marksmanship needed to employ the sniper weapon system, but will discuss certain steps needed to take to set up the weapon and optic. For this article, I’ll be using the M2010 Rifle that is currently employed by
the U.S. military.
APPROPRIATELY FIT RIFLE TO INDIVIDUAL FIRER
There are several adjustments that must be made both to the rifle itself and to the associated equipment to achieve a natural firing position. The sniper must experiment to find the adjustments necessary to best facilitate the fundamentals of marksmanship, and body structure.
Length of pull is the distance between the butt and the trigger. The sniper must determine the proper length of pull in all firing positions. What the sniper is desiring to achieve is the ability to pull the trigger straight back with a 90-degree trigger finger able to have a clean “break.” This must be checked in all firing positions to assure the firing shoulder does not need to be scrunched or the neck stretched to put the sights on target. If this occurs, it will create muscle tension and excessive movement.
Eye relief is the distance from the sniper’s firing eye to the rear sight or the Ocular lens.
To achieve proper eye relief, the sniper must keep his head as upright as possible, with his firing eye located directly behind the rear portion of the sighting system. This head placement allows the muscles surrounding his eye to relax. The best aid to consistent eye relief is maintaining the same stock weld from shot to shot. The scope must be adjusted forward or back to assure proper eye relief is established, and must be checked in various positions before zeroing so it does not encourage improper position.
It is important for the sniper to know the scope eye relief range changes with magnification. Knowing this can assist in awkward firing positions making obtaining appropriate eye relief challenging. Reducing scope magnification can increase the amount of eye relief required to obtain a full field of view, where increasing the magnification can have the opposite effect.
FOCUSING THE RETICLE ON A SCOPE
All reticle focus adjustments are made with the eyepiece. When pointed at the sky or a plain back drop such as a white wall, take a few quick glances through the scope at the reticle. If the reticle is slightly blurry at first glance the scope focus needs adjusting. This will cause undue stress on the sniper’s eye(s) over time.
It is best to look away from the scope while making focus adjustments as your eye will auto correct an image slightly out of focus. If your scope is equipped with a locking ring turn the lock ring so it allows the eyepiece to rotate freely. Make small 1/4 turn adjustments while looking away, and checking reticle clarity every 1/4 turn. Continue this process until the reticle appears clear and sharp.
If your eyesight changes, readjust the eyepiece. As we age, eyesight normally changes. You may want to check the sharpness of the reticle on your scope every time your eye prescription changes, to ensure it is still adjusted correctly for your eye.
ERRORS IN AIMING
Everyone makes occasional errors in aiming. Some common causes for aiming errors include—
- Shadow effects.
During aiming, the sniper must ensure that the telescope’s field of view is clear and shadow-free. Incorrect eye relief creates a circular shadow that reduces the size of the field, hindering observation. Crescent-shaped shadows cause the bullets to strike on the side opposite from the shadow.
If the sniper notices a shadow on the edges of the field of view (FOV), then he must find a head position where he can clearly see the entire FOV.
Affects the projectile’s ballistic trajectory; longer TOF (Time of Flight) equals an increased measurement of error.
Eliminating weapon cant may not be critical for large or close proximity targets but is crucial for accurate engagement of small targets, long distance targets, and moving targets.
As a general rule (for common cartridges), a 1-degree cant will produce 5 inches of lateral displacement at 1000 yards in the direction of cant and will also produce a small vertical point of impact displacement.
Weapon cant should be identified and corrected through the use of an anti-cant device for all engagements. Scope should be set with plumb bob to ensure the reticle is perpendicular to the ground.
NATURAL POINT OF AIM
Maintaining NPA may be difficult when engaging moving targets depending on engagement technique and range. When engaging in a fixed target sector, shooters should always set body position so that they can smoothly track the mover through the entire sector without binding up and disrupting
NPA more than necessary.
Shooters may have to adjust body position with an elbow lift during the engagement in order to maintain proper aim point on the target as it moves through the engagement sector.
Occurs when your eye is at the very edge of the exit pupil. To eliminate parallax in side focus adjustment scopes, follow these steps-
- The reticle must be clear (focused) before turning parallax knob. If it is not, follow the instructions under
“Focusing the Reticle.”
- With the firearm in a stable position, look through the scope, concentrating on the center aiming point of the reticle.
- Move your head slightly up and down and left and right. It is important to not move the weapon while making these head movements as it can cause the appearance of parallax when there is none.
- The aiming point must remain in exactly the same position against the target; if it moves, turn the side focus adjustment dial until it becomes stable.
- Reticle’s focal plane, causing the target image and the reticle to seem to be in two separate places within the scope. This makes the reticle seem to move across the target.
- A True Minute of Angle (TMOA) is equal to 1/60 of 1 degree of arc. Its size increases uniformly over range, but its angular value stays the same.
- At 100 meters the value of one TMOA equals 1.145 inches. At 200 meters, 2.290 inches; at 300 meters, 3.435 inches; etc.
- At 100 yards the value of one TMOA equals 1.047 inches.
- At 200 yards, 2.094; at 300 yards, 3.141 inches.
- A True Minute of Angle (TMOA) is also equal to 2.91 cm at 100 meters, 5.82 cm at 200 meters, etc.
- For ease of calculation and scope adjustments we round these numbers into Shooter Minutes of Angle (SMOA). A SMOA at 100 meters is equal to 1 inch; at 200 meters, 2 inches; at 300 meters, 3 inches.
- To demonstrate the error imposed by rounding a TMOA to a SMOA consider the process at 1000 meters. A TMOA at 1000 meters is 11.45 inches. By using the rounding process for ease of calculation a SMOA is 10.00 inches. The variation created through the rounding process is 1.45 inches at 1000 meters.
- A Mil (milradian) is another angular measurement.
- There are 21600 minutes in a circle. 6283.2 Mils to a circle.
- Finding how many MOA is in a mil (21600 min / 6283.2 mils = 3.438 MOA in one Mil).
- There are 3.438 TMOA per mil but for field rounding use 3.5 SMOA per mil.
The most fundamental requirement for good accuracy is having a reliable zero.
Shoot groups from different positions to see how much your grip, cheek weld, trigger control and sight alignment affect the rifles POI.
Common terms when zeroing are:
|Common terms when zeroing are:|
|Point of Aim (POA):|
|Point of Impact (POI):||Location where the bullet strikes the target|
|Shot Grouping:||Shooter’s ability to place bullet POI in the same location on the target|
|Mean Point of Impact (MPI):||Center point of all shots fired|
|No Wind Zero:||Weapon zero without compensation for wind drift|
|Slipping the Scales:||Process by which the optic’s scales are brought back to zero in order to indicate rifle data for a specific range with no wind correction|
|Zero Shift:||Scope adjustment applied to compensate for the POI shift which occurs when using a suppressor or Cold Bore.|
- Torque scope base and rifle
- Clean rifle bore with dry patch or bore snake
- Bore sight rifle barrel and optic (If equipment is on hand)
- Fire one round to confirm impact on target
- Adjust sights to move POI to POA
- Fire a five round group
- Adjust sights to move MPI to POA
- Slip scales
- Confirm zero with five round group
Things to remember when zeroing:
- Incorrect parallax will change your zero.
- Incorrect optical focus will change your zero.
- Changing your body position will change your zero.
TALL TARGET TEST
Un-calibrated sight adjustments are one of the most common problems in shooting. In most cases there is some amount of error in a scope’s turret or reticle. Like every measurement instrument, your scope needs to be verified and determine if the adjustments are accurate.
The Tall Target Test is a calibration exercise. It must be conducted at exactly 100 meters or that you measure and account for the exact range.
You must also ensure that you’re not canting your rifle. Leveling sights is highly important. By shooting the Tall Target Test with your scope level installed, you can verify true vertical scope tracking.
Shooting with a verified level rifle/scope promotes better wind reading because you have eliminated any unknown components of cant. Tall Target Test is follows:
- Set up a target board (at least 36” tall) with a vertical line drawn (confirmed with plumb bob or level) at 100 meters. Measure range with LRF to confirm actual range.
- Place an aim point near the bottom of the vertical line and shoot a group to confirm zero.
- Dial up (or hold) 30 MOA/10 MIL (based on your turret measurements) of elevation and shoot another group.
- Measure the distance between shot groups with a tape measure.
- Use the formula below (figure xx) to calculate your scope correction factor.
- Apply correction factor to any raw ballistic solution to account for scope tracking error.