Why Is My Rifle Scope Losing Zero?
Many gun enthusiasts know that to maintain the perfect zero for their rifle scopes over a period, they have to constantly rewind it. People wonder why the rifle scope loses its zero even when they haven’t used it.
There are plenty of reasons why rifle scopes lose their zero. It could be due to mechanical errors, cleaning issues or incorrect mounting. We understand that keeping a perfect zero can be tough. It is ideal to get it in perfect focus especially before you head out for hunting or shooting. In this blog post, we discuss the common reasons why your rifle scopes go out of balance and lose the zero.
What Does Zero Mean?
Before we discuss the reasons why the zero goes out of focus, let us understand what the zero means. Zeroing or focusing the rifle scope means aligning the scope with the bullet trajectory so that your bullets hit the intended target at the required distance.
You cannot manipulate bullets to go exactly where your scope shows. However, you can adjust your scope to point the crosshair to the exact spot where your bullets are going after every shot.
Rifle’s Range and Bullet Drop
The windage and elevation adjustments on your scope can be tuned to focus the reticle on the spot where the bullets are hitting. You will need to select a distance for the zero. A distance of 50 yards is generally considered ideal for a start. Gunners practicing for short-to-midrange shooting go for this range. If you are looking to shoot and hunt from a distance, then anywhere between 100 – 300 yards should be alright.
When you shoot a bullet from your rifle, the bullet should travel in a straight line from the bore axis and fly parallel to the rifle’s line of sight. However, gravity begins to pull it down as soon as the bullet leaves the gun. This causes a ‘bullet drop’ until it falls on the ground. This is why bullets do not travel in a straight line but an arc.
The bullet travels the fastest when it leaves the muzzle so the gravity’s pull is weaker. The bullet gets slower at a longer distance and the gravity’s pull is stronger, causing the bullet to fall at a faster rate.
What Causes a Rifle Scope to Lose Zero?
A rifle scope can lose its zero for a variety of reasons. If the rings have become worn out they can put your scope out of balance every time you shoot, causing it to lose focus. Cheap or low-quality scopes lose focus more quickly and some gunners have found them to be off by as much as 2 – 3 inches after a couple of hours of target practice.
The loss of zero for rifle scopes can be divided into four major categories.
Mechanical issues are the main reason why rifle scopes go out of focus. For example, if you increase or decrease the magnification power of your gun’s scope, the point of impact also changes. While the bullet may hit the target at a range of 200 yards, it may be off by a foot or more at a distance of 300 yards.
It all depends on how lenses are arranged inside the scope. Some of the newer scopes are built for shooting at specific distances and the aim does not shift by a lot at various powers of magnification.
Another issue is problems with the gun’s barrel droop. The barrel is what gives the gun trajectory. If it becomes even slightly angled, it can seriously put your shots out of focus.
The third cause of zero loss is when the vertical reticle is adjusted too high for shooting at a longer distance. The scope’s reticle is etched on a tube called the erector tube. When you make adjustments to the reticle, the entire erector tube is moved. There is a spring on the opposite side that becomes too relaxed and it does not hold the erector tube firmly in place, causing it to lose focus with each shot.
Most other mechanical issues for loss of zero take place in a similar manner. Every time you make a shot, the springs get lose or parts of the scope, mount or the gun become worn out, causing the scope to lose its aim.
Another reason why scopes lose their zero is that they are fitted incorrectly on the mount or that the mount itself isn’t put on the rifle correctly. Scope mounts consist of rings, screws, and the base; if either one of them is n0t screwed in securely enough, they can become lose with every shot, throwing your aim off balance.
Another problem is tightening the screws in too tightly. This can cause the base of the mount and the screw holes to get damaged.
Some gunners attach a mount that is slightly off the gun’s center because they cannot find a base for their gun. The mount is either slightly to the right, or left of the gun sights. To make up for the base that is off the center, they adjust the scope’s angle to the left or right to get the perfect zero.
When using this strategy, make sure that your scope is attached to the rings correctly, as it will always need to be slightly adjusted to one side from the center.
Cleaning and Different Ammunition
The condition of your rifle is important to maintain its scope’s zero. Even the slightest rust inside the barrel can have a big effect on the scope’s accuracy. Damaged or blocked barrels can also cause the scope to lose its perfect zero. Not only are they bad for your gun’s accuracy, but they are also quite unsafe. Corrosion or fouling may cause the mechanisms to fail or misfire
Your bullets should also be clean and measured. If you have any doubts about the condition of the firearm, you should not use it until it has been properly checked, cleaned, and repaired.
If you allow a small amount of fouling build-up in rifle, it will hurt the consistency and accuracy of your gun.
The fourth reason why rifle scopes lose their zero is because of mishandling during traveling. If you place your gun at the side, resting it on the scope, it can significantly put your zero out of focus. Too much pressure on the scope can also bend it, causing permanent damage to its aiming capacity.
One solution is to take the scope off from the rings and carry it in a handbag. This will ensure that your scope does not get bent during travel. It will also keep the lenses protected from dirt and damage.
However, just because you carry your scope in a backpack does not mean it cannot lose its zero. When you are fitting the scope on the rifle in the field, you may have to test it out to ensure that it is secured to the correct angle and tightness.
Another reason why your scope may be losing the perfect zero is due to the parallax. It is an inconsistency in the rifle scope that is visible when you look down the rifle scope. When you move your eye position to the left or right, the crosshair on your target will also appear to move slightly left or right. This means the reticle is not showing the exact location where your bullets will hit.
To hit the target, you will need to compensate and adjust your aim for parallax. The problem of scope parallax is more common in scopes with a higher magnification.
Do You Have to Zero Your Scope for a Hunt Every Time?
The answer depends on the condition of the scope and rifle and how often you go hunting. If you are going on a deer hunting trip for a week, where you will be shooting a dozen or so bullets every day, then you only need to zero your scope once at the start of the trip.
If you go hunting for a couple of days after a break of 2 – 3 months, then you will need to adjust the zero after every two or three hunting trips.
The quality of your scope and gun also plays a huge role in how often you need to adjust the scope’s zero. Good quality scopes can go for years without needing any adjustments with a barely recognizable difference in zero. Even the cheaper scopes can last at least a few hunting trips before you will need to readjust the zero.
In this blog post, we reviewed some of the reasons why rifle scopes lose their zero. Do you have more questions or something to add? Leave a comment below!