Scopes assist riflemen by allowing them to see more precisely at further distances. The power can range from 1.5x to 50x for conventional rifles. When placed on a rifle, it is often "bore sighted" from the gunsmith (or, if you mount it, it isn't sighted at all). When the gun first gets taken to the range, the rifle must be zeroed. Which means that at distance X the bullet will land exactly where the reticle is aimed (not counting for any wind or elevation changes). Standard combat rifles or varmint rifles are usually zeroed at 100 yards (we will assume, from now on, 100 yards is zero distance).
1.Determine how far off target a bullet lands, then adjust the scope accordingly . This is the most conventional way to zero the scope.
Most scopes have windage and elevation knobs which can be turned to compensate for inaccuracies. The elevation is usually on the top and affects the bullet's point of impact (POI) vertically. The windage is usually on the right side of the scope and affects the bullet's POI horizontally.
2.Most scopes have either mil-dot or ballistiplex reticle which allows the shooter to easily line up a shot at distances further than the zeroed point.
Most scopes come with a chart to show based on the bullet's caliber, velocity, and weight where to line up the reticle. While the weight and caliber are easy to mimic, the velocity is a very specific thing to a rifle. You will likely have to create your own chart for your rifle if you wish to be as accurate as possible.
3.Know that while military snipers practice adjusting the wind-age and elevation for the specific situation, it usually isn't practical for hunters or recreational shooters to precisely measure wind speed and other factors to the target and adjust the scope It is often best to do approximate calculations and hold-off the reticle, so re-zeroing the scope is not necessary. There are many factors that need to be taken into account when adjusting the scope, here are a few of them (in general order of priority)
- Distance to target needs to be calculated for zeroing of the scope. When not at your zeroed distance, bullet drop or rise needs to be taken into account (read about zeroing above).
- Bullet velocity affects the amount of bullet drop.
- Cross wind affects how far to the left and right the bullet will land. Under 100 yards, this usually isn't too big of a factor, but with a lighter bullet at 300 yards and a 5MPH wind, the bullet landing point can move up to a foot.
- Bullet weight is also a big factor, especially at longer distances. It will determine the maximum effective range of a bullet (since heavier bullets have better aerodynamic coefficients), thus bullet trajectory, and how much cross wind will move the bullet.
- Aiming at a target at a different elevation (even if only a few yards) than yourself is known asshot angle. It is another variable that needs to be taken into account.
- All the lesser affects are often not considered, but they can still influence bullet flight path.Head/tail wind affects the long distance bullet velocity and trajectory. The distance from the ground and ground temperature compared to ambient (air) temperature can cause bullet lift. Often after a hot day, when the ground is warmer than the air, there will be less bullet drop, and vice versa. Humidity and temperature also have minute affects on bullet trajectory. On extremely long shots (more than 1000 yards) even the curvature of the earth should be accounted for if a pinpoint-accurate shot needs to be taken.
- There are computer or PDA calculators which can calculate the exact landing position of the bullet based on all the information above (at least the major points). The calculators usually assume you re-zero your reticle. That is the best way to be perfectly accurate, but for target shooting where you don't need a one-shot-one-kill, re-zeroing can be a lot of hassle.
- If you do adjust the reticle positions, you should try to keep track of how many clicks in each direction were used, so at the end of the day, you can set the scope back at its zero.
4.Adjust the parallax (if available) according to the distance your target is at. Many scopes (especially adjustable-power scopes) allow the shooter to place the reticle on the same distance plane as the target. This is essential to take an extremely accurate shot.
- Most parallaxes have distances listed on them. Though these numbers are often good guidelines they are rarely accurate. Based on the distance of the target, the shooter's eye relief, and power of the scope, the parallax will change minutely. Parallaxes are often very difficult to adjust accurately, but with a little practice you will be able to estimate the parallax position based on the distance to target.
- A way to "cheat" the parallax is to place your head in a relief position where you can see black around the edge while viewing down the scope. Move your head and eye to make the black area even on all edges around the reticle.
- While the parallax is important for an extremely precise shot, a parallax set at 150-yards (the standard distance for fixed parallax scopes) at 1000 yards, the reticle will be at a maximum of eight inches off (at closer distances it will be much less — at 500 yards a maximum of an inch and a half off).
5.Align the scope properly by placing the cross hairs in the center of your target at your zero distance. You may need to compensate for distance, angle, or headwind by raising or lowering the cross hairs, keeping the center line on target.
TIPS
- Depending on the selected bullet and rifle(you must do research or testing to find the case with your setup) the zero range may cause the bullet to be below the reticle before zero, then above after zero, and eventually falls again to (at a different distance) be lined up with the reticle again (this may be 120 yards or 300, and it will likely change from rifle to rifle, even in the same caliber). Another, more common, scenario is that the bullet climbs sooner, and from (say) 40 to 100 yards is above the reticle, it then falls to meet your zero, and from then on (100 and more yards) is below the reticle.
A few standard cross hairs.
No comments:
Post a Comment