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Understanding more about scopes and angles

The right mounts and optimal scope setup can make all the difference

If you are a shooter that relies on optics to get the job done, then you know exactly why your mounting hardware and scope setup is so important. You may have a great scope and a great airgun, but if the equipment that connects the two is not up to par, and it’s not setup correctly, then you’ll always be shooting below your true potential.  In this article we’ll look at why it’s so important to have the right mounts and setup to get the best results.

Get it straight.

Do you remember sitting in geometry or trig class wondering “when will I ever use this stuff in my everyday life?”  Well, geometry is all about angles and trig is all about triangles.  Believe it or not, when you mount a scope to your rifle you’ve just crated a right triangle.  If you’re fortunate, you’ll be lined up dead center on the receiver, where the center line of the scope is in perfect sync with the bore of your gun.  If not, then not only are you creating a triangle, but you’re also adding a 3rd angle left or right.  So what does this mean practically?

Scope Height Chart 1

Let’s start with the assumption that your mounts are perfectly aligned with the bore of your airgun and you’ve sighted your scope at 20 yards.  As you shoot at objects closer than 20 yards, the point of impact will be below your scope’s aim point.  This is because the horizontal leg (the bore of your rifle) has yet to intersect with the hypotenuse (the sight line of your scope) in our right triangle.

When you shoot at targets beyond 20 yards, you’ll see the pellet impact above the aim point of your scope. This is because the sight line of your scope continues downward as the bore continues on a straight path, that is until gravity takes over and the pellet begins to drop.  This is why a mil-dot or some other range estimating reticle is so helpful.  If you know where the pellet impact will be, as related to your distance to the target, you can adjust your aim point and put lead right where you want it every time.

Scope Height Chart 2

One way to reduce this effect is to always make sure to match the proper height mounts to your setup.  The closer you can get the scope to the receiver (the bore of your airgun), then the less of an angle you have to deal with.  Scopes with a 32mm objective can generally use medium mounts, while scopes with 40mm and larger objectives may require high mounts, especially if you are going to use scope caps.

Proper Setup helps

Another way to reduce the impact of this effect is to find the optimal sight in range for your particular airgun setup. To do this you’ll need a few pieces of information.  First, you’ll need the true velocity of the pellet you’ll be using with our airgun.  The only way to get this is to use a chronograph.  A chronograph is an invaluable tool for the serious airgunner.  Next you’ll need the ballistic coefficient of the pellet you are using.  There are tables with this information available on the internet.  If you can’t find it, you may try contacting the manufacturer of the pellet to see if they can provide it to you.  You will also need the distance, or height, of the sight line of your scope as related to the bore of your airgun.  Lastly, you’ll want to get Hawke’s ChairGunPro software.

Once you’ve got all that data, you can plug in the variables and find your optimal sight in range for your scope as related to your particular airgun and scope setup.  This can allow you to have the flattest possible trajectory and help reduce errant shots due to extreme scope angles.  This technique is really useful for small game hunters that may be taking shots at various distances.

Optimal Scope Range Chart – Optimizing the scope sight in point yields  a 1″ killzone around the aim point that ranges from 12.7 to 50 yards!

Practice, practice, practice

With the right scope, right mount, and optimal sight in, all that’s left is practical experience.  Working out all the above may not yield perfect results, but it will certainly get you much closer to the target than setting things up in a completely arbitrary manner.  Once you’ve spent some time testing your configuration, it may only take a couple of minor tweaks to dial it all in.

Oh yeah, that 3rd angle…

All of this works pretty well so long your mounts are 100% lined up with the bore.  Unfortunately this is rarely the case.  Universal scope mounts have to allow for varying sizes of dovetails and thus they may lean one way or the other slightly.  When this happens, your point of impact will change not only on the vertical axis, but will also transverse the horizontal.  The only way to address this issue is to find mounts that are 100% square on your receiver.   This effect is usually pretty minor in the big picture and may not really impact general hunting uses, but in competition, it very well could make all the difference.

Scope Height & Angles Chart 3

Whether plinking in the back yard or competing in bench rest and field target, having the right scope setup can make your whole shooting experience that much better.

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If you are a shooter that relies on optics to get the job done, then you know exactly why your mounting hardware and scope setup is so important. You may have a great scope and a great airgun, but if the equipment that connects the two is not up to par, and it’s not setup […]