By Rich Saito
Gone are the days when rifles were the sole purview of SWAT teams across the nation. They have become a national standard for the patrol officer with good reason. Rifles are generally easier to shoot more accurately than handguns, offer superior terminal and exterior ballistics, and are capable of precision at extended distances. Combined with a reliable red-dot optic with a consistent zero, these platforms can be a valuable force multiplier.
Yet a recurring issue among many end users is point-of-impact (POI) shifts that become increasingly noticeable over weeks and months. Sometimes, those shifts are minor, equating to less than ¼ MOA. Other times, however, in extreme cases, shifts of several MOA are possible across windage and/or elevation. A properly mounted, trustworthy optic should hold zero across thousands of rounds and routine handling. If not, the rifle is telling you something, and ignoring it creates a potential avalanche of liability.
What is a zero?
In its simplest terms, a rifle zero is the process of aligning the rifle’s point of impact with the optic’s point of aim at a specified distance. Those distances are typically 25, 50 or 100 yards, but they can be whatever the user decides, with the understanding that each comes with pros and cons.
The 50-yard zero is often cited as the most versatile zero distance based on the flatter trajectory of the 5.56 round. In any case, the rifle zero is a “converging zero.” Because the optic sits above the bore, the projectile’s trajectory intersects the optic’s line of sight at predetermined distances.
Chasing the zero
Your rifle zero is everything. The user needs to have confidence that the bullet goes where expected, notwithstanding mechanical offset caused by the optic sitting above the bore. A zero shift is obviously problematic in crisis mode when precision fire is necessary to end a conflict and rounds do not travel as anticipated.
We have all likely experienced this differential. We zero our rifles at the agency range under the guidance of an experienced training staff. Impact groups are tight and all in the designated target area. Rifles are cleaned and stored in some vehicle storage compartment until ready to use or the next training day.
Fast forward six months later. We attend a training session and discover that our POI has shifted several inches below the target. We scratch our heads and swallow our pride as the range officer publicly ridicules us in front of our peers. Another 45 minutes is then spent off to the side while the irritated range officer repeats mantras about smooth trigger squeeze, sight picture and natural point of aim.
Empirically, the shift occurs at all levels. The most experienced, skilled shooters can see these deviations just like the novice. The causes are numerous and often difficult to isolate without deliberate evaluation.
User error
User error does not suggest the shooter does not know how to put a dot on a target and pull the trigger, but rather is inducing a shift based on simple mechanics. Most errant shooting outcomes can be attributed to user error. In other words, we do something that causes us to miss.
The most common fault is typically the manipulation of the trigger, an irregular pull that causes movement of the rifle before the round can leave the barrel. The quickest way to diagnose this potential cause is to assess shot groups on paper. A large spread of holes indicates improper trigger engagement or an inconsistent rifle-body weld. The shooter is causing the rifle to move on every shot.
We see this occur when triggers are pulled too rapidly, shooters repeatedly reacquire the trigger press and/or shooters shift their grip, cheek weld or shoulder weld after each shot. Consistency is key. Every round fired should be from the same positioning with the same trigger press as the one before. Natural point of aim principles help build this consistency, especially with windage shifts.
Another suggestion is to ensure the rifle is stabilized to its fullest extent using a solid support like a bench rest. Shooters should be slick (i.e., not wearing gear) and be as comfortable as possible. Proper positioning includes aligning the spine behind the rifle in line with the barrel, deep engagement of the stock into the shoulder and keeping the shooter’s eye centered through the optic tube. The goal is to eliminate, as much as possible, all the variables that could cause inadvertent movement of the rifle.
Remember, we are mechanically establishing a convergence of a predictable bullet flight path with the dot set on a specified target. In theory, a properly zeroed rifle should maintain the same mechanical zero regardless of shooter, although individual shooter mechanics can still produce minor deviations. That being said, agencies should avoid issuing random rifles at the beginning of a shift. Although the established zero should be the same across all users, each shooter handles the rifle differently, creating opportunities for POI shifts.
If the shot group on paper is tight, with all rounds roughly within an inch of one another, but missing the designated target, this indicates a zero issue. We need to explore other potential causes.
As a caveat, one to three rounds on paper are insufficient to establish a proper zero. When mounting a new optic, a few rounds can be used to gauge a general idea of accuracy relative to the target. But shooters are human, not robots, so we expect there to be some level of inconsistency in the grouping, i.e., an occasional “flyer.” A few rounds typically do not provide enough data to confidently assess a group. A five-round shot group is a solid number for evaluation.
Mounting failures
An often-overlooked cause, and likely one of the most common, is the interface between rifle and optic. How the optic is mounted to the rifle is a critical component in ensuring the desired consistency for a zero. Improper mounting procedures can result in huge deviations downrange.
Rail-mounted optics are prevalent among major manufacturers with torque specifications for mount-to-rail clamps. Short-changing or inconsistently applying these specs will result in movement of the optic, however slight. But even a slight movement means potentially huge variances in POI. Also, with bifurcated top rails, mounting an optic straddling the split invites movement.
Clamp screws that go into the rails should be pressed firmly against the rail interior before tightening.
A popular accessory is an optic riser, which elevates the optic to align more naturally with the eye when shouldered. These risers require additional screws to mount the optic to the riser itself, opening the possibility for improper application of torque. Thread lock should be applied in accordance with manufacturer specifications. Hand-tightening or relying on “feel” is insufficient and should not be standard protocol.
Ammunition
Most departments distinguish between “range ammo,” used for training purposes, and “duty ammo,” used for actual deployments. These two ammunition types are usually different, with range ammunition typically consisting of inexpensive ball, or full metal jacket, projectiles. Good duty ammo is usually a slightly heavier round with a bonded core to provide sufficient penetration through barricades, especially glass. These two rounds are not created equal and are affected differently in flight and upon impact.
Final zero confirmation should always be conducted with duty ammunition. An argument can be made to maintain more consistency by pulling ammo from the same lot number. However, at shorter zero distances, the differences will likely be negligible. But using a lighter FMJ to zero will not result in the same POI as duty ammo. Shifts are commonly seen in elevation, although windage deviations can also occur depending on barrel harmonics and projectile characteristics.
That difference can be marginal or significant. However, because we are attempting to establish a predictable point-of-aim-to-point-of-impact relationship, we should not tolerate “close enough” or “good enough for government work.”
Mechanical issue
Not all departments have the luxury of issuing new, pristine rifles to their personnel. In reality, department rifles may have well over 15,000 rounds through their barrels, with limited, if any, maintenance performed over the years. These systems get passed down through agency attrition, with the end user issued, in some cases, a 15-year-old rifle.
Barrels eventually wear out, barrel nuts get worn or loose, and handguards and rails become damaged. In rare instances, manufacturers may ship rifles that fail to meet factory standards or are built to the lowest quality specifications. In any case, these represent hardware issues that can only be remedied with a new system or replacement of damaged or worn parts.
A former sniper instructor preached the importance of maintaining fouling-free barrels. After every session, barrels were to be cleaned until no signs of copper jacketing or fouling were evident, with the notion that a first cold-bore shot would be consistent and predictable.
Personal experience, as well as empirical data, seems to suggest this is less of a concern than advertised. While a clean rifle should always be maintained to avoid excessive carbon buildup on working parts, a dogmatic approach to cleaning the barrel is a needless exercise. Precision rifles have proven capable of maintaining tight groups regardless of excessive barrel-cleaning procedures.
Optics are ruggedized but not necessarily bomb-proof. Reputable manufacturers have established a track record of reliability that provides the end user with confidence that any divergence is likely not equipment-related. However, with all other factors eliminated, a constant shift of zero points to faulty gear. Do not opt for the cheapest option. Spend the money and buy reliable, proven optics.
Environment
Bullets travel a predictable flight path based on the conditions on any given day. Variables such as temperature, humidity, density altitude and wind all affect how a bullet travels through the air. Some areas of the country see drastic environmental changes throughout the year, the Northeast for example, where conditions range from hot and humid during the summer to freezing in winter.
Environmental changes become increasingly significant as distance increases. While a 50-yard zero may only experience minimal deviation, temperature, density altitude, humidity and wind can produce meaningful shifts at extended distances.
Storage
Storage considerations are an enigma. On the one hand, duty-built rifles and optics are meant to withstand a certain level of rough handling. However, from an empirical standpoint, there appears to be a correlation between how rifles are stored in duty vehicles and the maintenance of a zero.
A system that is placed haphazardly in the trunk or storage box is likely going to result in equipment movement with repeated slamming inside the compartment. From a common-sense point of view, repeatedly impacting a mounted optic day after day is likely to affect the zero.
Unless mounted in a rack during a shift, rifles should be securely fastened in a storage box or trunk. Consider foam inserts for storage boxes or a hard case that can be secured to the vehicle.
Properly diagnosing any problem requires a basic understanding of how the system works. When assessing shifts in a zero, we have established a litany of possible reasons. User error is often the most controllable and likely culprit and should be one of the first considerations, especially with inexperienced shooters.
When the phenomenon occurs with seasoned officers who know their way around a rifle, attention should be given to the other influences discussed here. Equipment reliability is dependent on user maintenance. In the case of a rifle zero, confidence is built through consistent verification under repeatable conditions conducted as often as feasible.
About the author
Rich Saito is the co-founder of Cadre Consulting Group, a South Florida-based law enforcement training company. He currently serves as a sergeant with a major law enforcement agency in the region. Saito has nearly 20 years of SWAT experience and has participated in more than 1,500 tactical operations. He currently serves as a SWAT team leader and supervises the unit’s sniper element. Throughout his career, he has also served as a rangemaster, training sergeant, and fugitive unit supervisor.
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