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Thursday, November 24, 2011

Scope Reticles 101


     Which scope do you recommend? I get asked this question several times a month. I wish the answer was as simple as the question. There are several factors we should consider before making a choice. The next few questions will help clarify the proper response to the question.

     What gun is it going on? Is it a semi auto 22 or a 300 WM bull barrel target rifle? Is it a 30-30 lever gun or an AK? The type of gun and the caliber are important factors in the scope and reticle choice. What do you plan to do with the gun? Self-defense has different requirements than hunting or target shooting. What caliber is the rifle? A 22 rim fire runs out of energy past 300 yards. What are the external ballistics of the round?  How fast does it loose velocity?

     It makes no sense to put an optic designed to shoot a thousand yards on a rifle/ cartridge that is not accurate at that distance. Here is an example. The 7.62x 39 cartridge velocity is approximately 1150 fps at 500 yards; at 600 it falls below 1000 fps. Generally 1000 fps is about the speed at which rifle bullets become unstable. This instability causes the bullet to yaw and wobble. The wobble changes the flight path. Based on my experience unstable flight path can vary greatly. I am talking about variation by feet, not inches. If you add in weather and wind factors the variation is increased. So a 7.62x39 or a 30-30 would not be a good rifle for a 6-20 x 50 target scope. A 1-4 or 2-7 or a low power fixed scope would be a better choice for these calibers.

     On the other end of the spectrum is the 338 Lapua. This round at 1000 yards still has a velocity of 1680fps. This means the cartridge is accurate well past 1500 yards. Installing an Eotech red dot or a 3-9 power scope is limiting the capabilities of the cartridge. Generally speaking having 1 power of magnification per hundred yards is good if you are shooting man size targets.  If the man ducks behind cover or goes prone you may need more magnification to find and shoot this now smaller target. Higher power will also aide in range estimation. On the down side, higher power can amplify movement as the shooter moves the gun. It can also be difficult to shoot through the mirage on a high power setting.

    Now that we have the basics as to what we want to do with the gun/ammo scope combination (also called the weapon system). We can look at reticles for the scopes. There are hundreds of different reticles available for scopes. The early scopes had crosshairs and nothing else. Since the invention of crosshairs in scopes man has looked at ways to improve the basic idea by adding thicker lines or removing a portion of the crosshairs (also called stadia lines). Today scopes have 4 categories of reticles.

       Standard Reticles Fine, Crosshairs or Duplex

       Illuminated Reticles; Eotech, Aimpoint or Trijicon

       Hold Over recticles; a bullet drop compensator type

       Ranging reticles; Mil-dot or MOA hash marks

      (Combinations of 2 or more can also be found.)

 

    This article will examine standard reticles and illuminated reticles.

    The standard reticles group includes the t-post, target dot reticles. The stadia lines may be tapered or have two different widths. Standard recticles are used to zero a rifle at a specific distance. That is about as basic as it gets. The turrets on the basic scopes normally do not have numbers or revolution marks to adjust them to different zero points. They are meant to be zeroed and left alone. These types of scopes work well on rim fire and hunting rifles designed for 200 yards or less. With some practice the shooter can use them for longer shots by holding over on the target. They have no value in ranging to the target and adjusting for wind or weather changes.

     The variable power scope with a duplex type reticle can be used for ranging by using the points where the stadia line reduces from thick to thin. This method works by adjusting the magnification so that a known object will fit the reticle between the horizontal line and the point where the vertical line changes width. This requires practice and the shooter should develop a range card to record this information.

     Here is an example. Your target is a deer.  It’s size from the top of the shoulder to the bottom of the belly is 18 inches. Now use the zoom to set the horizontal line on the top of the deer’s back and the point on the vertical line at his belly. Now determine the power setting. Reference this number to your range card and read the distance to target. Then you can use the hold over you established during practice to make a hit. For this to work the shooter must put in the time to gather the information and build the range card. This same principal works for many different types or styles of reticles.

    The newest style of reticle is an illuminated reticle. There are 3 sources of illumination, battery power, fiber optics, and tritium.  Combinations of the three can also be found. The most simple of these is the battery power models with a round dot in the center of the lens. The red dot reticle can vary in size, shape and clarity. With variable power scopes and red dot scopes the quality of the glass can vary. Better quality glass will result in a crisp edge to the dot type reticle.

     Try this little test. Pick up a cheap red dot and turn the power up to its highest setting. Notice the dot is not perfectly round; it can look like a star. Or it may have streamers coming from the center. While taking a sight picture rotate the red dot. See if the streamers rotate with the scope body. No streamers means the glass is of high quality. Another test is to take the red dot scope into the full sun and check to see if the dot is visible. In some of the economy models the dot will almost disappear. Next look at in in very low light. The dot should be visible but not so bright that you can’t see the target past the sight. The size of the dot makes a difference as well.

     An EO Tech has a 1 min dot in a 65 min circle. These are designed to use the small dot for accuracy and the large circle for speed. The Aimpoint models have a 3.5 min or 8 min dot. For a rifle or carbine I like the 3.5 min dot. Why the smaller dot on a carbine? The dot covers up 3.5 inches of the target at 100 yards or 7 inches at 200 yards. I can still make a head shot at 200 yards with it. The 8 min dot would be 16 inches at 200 thus making a head shot hard.  The average head is 8 inches wide. The Leupold Delta sight uses an illuminated triangle instead of a round dot. This gives the shooter an option: fast shooting at close range when referencing the entire triangle on target or using the top point of the triangle if a more precise shot is needed. I recommend zeroing the rifle at 200 yards to the top point of the triangle or the top edge of the round dot. Bushnell has a multiple reticle red dot that has a circle dot, a small dot and “T” style reticle. The shooter can select all three if needed.

     Battery life is a big factor when using a red dot scope. The first models lasted about 24 hours before the battery died. The latest model Trijicon RMR will run more than a year before the battery dies. The Leupold has a motion sensor that shuts down after 5 minutes of no movement. The standard red dot sights do not have any magnification. Therefore, long range precision is no better than when using sights.  If these are used on a rifle the shooter is limiting the performance of the weapon system. Power failure while using battery powered sights is the main reason for having back up iron sights on a gun. The other option is to use the scope itself as a huge ghost ring and put the target in the center and press the trigger.

     Fiber optic illuminated red dot sights have the advantage of not needing a battery for illumination. No battery means no power failure. A benefit of the fiber optic system is the brightness level automatically adjusts to the ambient light. This also means it is always on. A few models even have a shade so the shooter can block some of the ambient light to reduce the reticle brightness. There are 3 styles of reticles for fiber optic scopes, a solid round circle, a triangle and a chevron (an inverted “V”). There are also color options of red, green and amber. I have used all three and I like the green the best. The red can disappear on a red target or on the red dirt here in Georgia. The green is a fluorescent green that has a good contrast in foliage. Also green is in the middle of the light spectrum and is easier for the brain to pick up. The amber blends in on fall days with flat light or in reduced light. To me green is the easiest color to pick up in a wide variety of light conditions. The size of the reticle is just as important on a fiber optic scope as it is on a red dot scope. Fiber optic scopes have one big advantage; the availability of magnification with them. There are fixed power and variable power scopes available with fiber optic reticles.

       There are a limited number of scopes with tritium illuminated reticles. They work well in low light but are not bright enough by themselves to work in sun light. Normally these are combined with fiber optics to give the shooter a sight in very low or no light. One down side to tritium is they do not last forever. The half- life is 12 years.

     For a fighting rifle I would only use a scope that will continue to work when the battery dies. If the battery dies and I can’t use the scope my effectiveness as a rifleman just diminished. We should all have the knowledge and skill to point shoot the rifle in CQB without the use of any sight system.

     We covered the 2 basic types of reticles in this article. Both have their good points and drawbacks. Remember any time you get to look through a scope outdoors take the opportunity to learn about the scopes. Learning experiences are valuable specially if they are free.  Part two of this article will cover hold over style reticles and ranging reticles.

Please join me for the Guerrilla Sniper I in Blakley GA March 8-10

 

Scott Vandiver

SI Staff Instructor

www.centerfiretraining.com

 

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The Suarez International Blog is a "warrior lifestyle" publication dedicated to the modern excellence-seeking martial enthusiast. Every article and video will feature the most up to date weapons, tactics, technology, and training methods available today. Not limited to merely "guns", we include articles on international adventure travel, extreme physical training, and living well in the modern world.