HFT – Scopes Explained

I was recently chatting to the guys at ‘In Your Sights’ (THESE GUYS) about scopes and HFT. Specifically they were interested to know what features I thought were important for beginners, or people crossing over into HFT for the first time. 

This got me thinking about all the things I wish I’d known when I was first starting out. The list grew and grew, and I’ve ended up splitting this post into three parts to try and cover it all properly:

  1. Scope features explained
  2. How to set up your scope
  3. How to use your scope for HFT

This post is Part 1, and I’m aiming for one post per week on this.

There’s quite a lot of detail here. If you don’t have time to read it all, you can skip through, or even to the end for a quick summary. But come back and read the rest later on. There’s a lot of questions I’ve had from people, that I’ve tried to answer.

The question I asked myself was, what scope do I need for HFT?
This is a tricky question and doesn’t have a straightforward answer. However we can use the rules of HFT, and a bit of experience, to help narrow it down a bit.
Back in my quick introduction to HFT (SEE HERE) I gave you all a link to the UKAHFT rules (LINK HERE). From this we know that from the first shot to the last, we are not allowed to adjust the scope in any way.

So what adjustments are available, and how can this help us pick a scope?
The next two lists are the main fixed, and adjustable parts of a scope:

Fixed

  1. Objective lens diameter
  2. Reticle
  3. Eye relief
  4. Tube diameter
  5. Focal plane
  6. Length
  7. Weight
  8. Lens quality and coating

Adjustable

  1. Ocular lens adjustment
  2. Magnification
  3. Elevation turret
  4. Windage turret 
  5. Reticle illumination
  6. Parallax (objective)

Lets look at the fixed parts of the scope first. These are important to understand because you can’t adjust them later on. Once you’ve made a decision you are stuck with it. They can also make a real difference to your shooting.

Objective lens diameter

This is the last number in the description of the scope. For example a ‘3-9×40’ scope has a 40mm objective lens diameter. What you have probably already heard is that the larger this number is, the more light gets gathered up by the scope. So surely bigger is better? Well no, not really.
What we actually need to consider is something called the ‘exit pupil diameter’. This can be thought of as a hole that the light from the scope has to pass through before it gets to your eyes. A bigger hole will let more light through. You can actually see this if you hold a scope at arms length and look through it. You should see a bright circle in the middle. That’s the exit pupil.

The theoretical exit pupil of your scope can be easily calculated. Simply divide the objective lens diameter by the magnification you are using. Lets say we are buying a scope for HFT, and we already know we want to use 10x magnification. But we have a choice of 32mm, 40mm, 44mm and 50mm objective diameters. Their exit pupil size will be:

  • 32 ÷ 10 = 3.2mm
  • 40 ÷ 10 = 4mm
  • 44 ÷ 10 = 4.4mm
  • 50 ÷ 10 = 5mm

So the statement above was true. The bigger 50mm scope has a larger exit pupil, so more light can get through. However this isn’t always a good thing. Your eye also has a pupil size, and the different between the two can cause parallax errors. 
If your scope is letting through 5mm of light, and your pupil is only 3mm big, your eye can move up and down by 1mm and you will still see a perfectly clear image. In this case you will be causing parallax error and have no visual clues that it is happening. (Later on in this post I will explain what parallax error is and why it’s a problem in HFT).
However if your scope is letting through 3.2mm of light, you will only be able to move your eye 0.1mm up or down. This means you will cause less parallax error before you see there is something wrong.

How big is an adults pupil? According to the ‘National Centre for Biotechnical Information’, a normal adult pupil will vary from 2mm to 4mm in bright light. In dark light this increase to 4mm to 8mm.
CLICK HERE FOR SOURCE

As we tend to shoot HFT during the day, lets assume 2mm to 4mm is likely. In this case the 50mm scope is too large. The extra size is not helping your view, but could be causing accuracy problems. This is one of the main reasons you are more likely to see the smaller objective scopes being used round an HFT course.

Reticle
Luckily this is easier to explain than the previous section! The reticle (also known as the crosshair) is the vertical and horizontal markings you see through the scope. This can vary from a the basic ‘solid lines making a cross’ to having multiple extra lines, dots and dashes. Some examples are:

Duplex (a.k.a 30/30)

Mil Dot
1/2 Mil Dot
Hawke AMX
MTC AMD
MTC SCB2

Some people prefer a very simple, uncluttered view. Other people like to have as many aim points and additional markings as possible. Really the best thing to do is to look through a few and make up your own mind about what suits you best. 
However I will say that I think a mil-dot scope is essential for beginners. This means there are equally spaced markings on the horizontal and vertical lines. These markings are 3.6 inches apart when looking at a target 100 yards away. However this can change depending on if the scope is first or second focal plane. (Focal plane covered further on).

Because the trajectory of airgun pellets is relatively loopy, we often need to aim above or below the target to actually hit it. Having mil-dots gives you a reference point for how high or low to aim.
I personally prefer a half mil-dot scope which gives you twice the amount of reference points. 

Eye Relief
By definition, eye relief is the ideal distance from the rear lens of the scope to your eye to give you the maximum viewing angle. When set correctly you will have a clear and sharp sight picture right up to the edges of your view. If set incorrectly you will see a blurry black ring all around the edge (eye too far away), or a crescent of black at one edge (eye too close). This blurriness is known as ‘vignetting’ and you don’t want it. Hopefully the following images will make it obvious what you should be looking for.

The amount of eye relief needed is specified by the manufacturer. Traditionally this is a few inches. This gives enough space between you and your scope to stop you getting a black eye when using high powered rifles. On airguns we don’t need as much protection from recoil, but we still usually get a couple of inches.
There are some airgun specific scopes available with very little eye relief. The benefit of this is an increased field of view. i.e how much of your surroundings you can see through the scope. The downside is that it can be difficult to mount on some airguns, because the scope rails often don’t extend far enough back. They can be made to work though, and plenty of people have success with them.

Tube Diameter
This is the size of the main body of the scope, where you attach your scope mounts. You will have two choices. 1 inch, or 30mm. There seems to be a long running opinion that 30mm tubes are better because they are larger, and therefore let more light through the scope. This might be true but have another look back at the exit pupil calculations from earlier. At 10x mag, we are only getting 3-5mm of light through the scope anyway. For the 30mm tube to actually let more light through, the exit pupil needs to be greater than 25mm. This means a 50mm objective lens, at 2x mag or less. Very limited benefit there then!

I’m not saying there isn’t a benefit though. The larger tube allows one of two things (or maybe a bit of both). The walls of the scope can be thicker, which makes the scope stiffer for added strength. Or larger diameter lenses can be used inside. Larger lenses generally perform better than smaller ones in terms of clarity and sharpness.
For a beginner to HFT I wouldn’t spend too much time looking at 30mm scopes. There’s no doubting they would be nice to have, but they are not essential. 

Focal Plane
This only applies to variable power scopes, and there are two options. First Focal Plane (FFP) or Second Focal Plane (SFP). The physical difference between the scopes is where the reticle is located. 

SFP scopes are more common. Here the reticle is located at the back of the scope with the magnification ring. When you zoom in or out the target gets bigger or smaller, but the reticle stays the same size. I’ll use a 40 yard target as an example. At 10x magnification, I need to aim 1 mil-dot above where I want to hit. If I reduce the zoom to 5x, I now only need to aim 0.5 mil-dot above the target. The target has effectively shrunk in comparison to the reticle. This also means that the mil-dot spacing of 3.6 inches per 100 yards is only valid at one mag setting. 
FFP scopes are less common. Here the reticle is located behind the objective lens at the front of the scope. In this position, when you zoom in or out the reticle increases or decreases in size at the time as the target. This means that the 40 yard target will always be 1 mil-dot, regardless of how much magnification is used. With this scope, the mil-dots will always be spaced at 3.6 inches per 100 yards.

FFP scopes are great if you change your mag setting on a regular basis, because you can always use the same aim points. With an SFP scope you will need different aim points for each magnification. However in HFT we aren’t allowed to change this. If you are only interested in target shooting, I wouldn’t be too concerned with what focal plane your scope is.

Length
This dimension is self explanatory, and most of the time you can probably ignore this. The only time I think it cause a problem is if you have a very long scope on a spring powered airgun. With a springer you will either have a break barrel, or sliding breech where you have to insert the pellet. If the scope covers up this hole then it could get a bit fiddly.

Weight
As you would expect, the larger scopes with more glass in them will be heavier. If you have an airgun that is already heavy, adding a massive scope might make it unusable for you. Having a very heavy scope on high mounts also introduces the possibility of ‘cant’. This is the rifle tipping over at an angle which can throw your shot off target. 
However the weight can also be positive. For standing shots, additional weight tends to make the shot more stable if you have correct technique. On a springer, the weight can also help to dampen the recoil.
However at the end of the day, I would say the weight is less important than the other factors mentioned in this post. I would probably only consider weight if I was torn between a couple of scopes and couldn’t decide.

Lens Quality and Coating
This isn’t really an option that you get to chose, but is more a function of paying extra money. A higher quality (i.e higher price) scope will tend to have higher quality lenses, and better/more anti-reflective coatings applied to those lenses. Why are these important thought?

The lenses themselves can be very high precision items. Their quality can be affected by the quality of glass used, how it is cut and how it is finished (grinding/polishing etc). If you buy a £30 scope from ebay, you can’t expect too much care to have gone into the manufacturing of the lenses. Poor quality lenses will have a cloudiness  or hazyness that no amount of coatings can fix.

Anti-reflective coatings pretty much do what they say on the tin. Normally when light travelling in air meets glass, most of it passes straight though, but some of it is reflected back off the surface. This also happens when the light comes out of the glass again and meets the air. So for every piece of glass in your scope, there are two opportunities to lose some light to reflection. The amount of glass per scope varies with each model, but you can probably expect 6, 8 or 10 glass elements. This can add up quite quickly into a lot of light lost, which would result in a dull and blurry image.
Anti-reflection coatings prevent this light from being lost, so more of the original light makes it all the way through the scope until it meets your eye. The better the quality of these coatings, the better this whole process works, and the clearer your final image will be. For more information there is a great article all about lens coatings HERE

At the beginning of this post I said that we aren’t allowed to fiddle with the scope in HFT, so surely we don’t need any of the adjustments on offer? Actually they are very useful (even essential) to make sure the scope is set up correctly for you and your airgun.

Ocular Lens Adjustment

This is essential and should be a feature of every scope you see. The reason for this is that our eyeballs aren’t all the same. They vary in shape and size which is the reason we don’t all have 20-20 vision, and some of us need glasses. So when we look through a scope and see the reticle, it focuses differently for each person. 
The ocular lens adjustment allows us to focus the reticle specifically for our eyes. Having this set incorrectly can cause focusing issues later on. It is located on the eyepiece of the scope, and is simply adjusted by winding the collar in or out.

Magnification (Mag/Zoom)

Almost all modern air rifle scopes have adjustable magnification. Usually in a range like 3-9x  at one end of the scale, to 10-50x at the other. But remember, for HFT bigger is not always better! An £800 scope at 50x mag might make that 45 yard target much easier to pick out, but the next one at 8 yards will be almost impossible to see, let alone shoot at. 
Finding the correct magnification for you will need a bit of experimenting. The ideal way to do this is to go to a club which has some HFT style targets set out. Using a rangefinder, or asking other people, find a target at 8 yards and another at 45. Now look at both targets at various different magnifications.
A good place to start is 10x, and is what a lot of people eventually settle on. This tends to give a fairly good compromise between long range and short range visibility whilst allowing a bit of blurriness to help range finding at 8 and 45 yards. 

There are fixed power scopes available that are generally set to 10x magnification. But as a beginner, I would go for variable power. You will learn a lot just by experimenting.

Elevation and Windage Turrets

Used to move your reticle up/down/left/right so you can set and adjust your zero. This is the most necessary adjustment which is found on every scope. The turrets themselves may be hidden underneath screw on caps, or exposed, and will click round in small increments. Each increment will equal a set distance that the reticle will move, for example 1/4 MOA (Minute Of Angle) per click. This would be equal to 1/4 inch at 100 yards.
The main difference between lower end and higher end scopes, is the accuracy of each click, and how well mechanism is designed and built.

Reticle Illumination

This turns on a coloured light inside the scope (usually red or green) which lights up the reticle. This can be useful in low light conditions, for example dawn or dusk hunting scenarios. Personally I don’t think its very useful for HFT and I don’t think I’ve ever used mine round a course. 
Of course other people may think differently, so it’s probably best to try one out first if you aren’t sure.

Adjustable Objective (a.k.a Parallax)

This adjustment will change the distance at which you get the sharpest focus. For example setting your objective to 20 yards, will make your 20 yard target crystal clear, (that’s the theory anyway). It also effects what is known as parallax error. This really deserves a whole post (which it will get) but I’ll try to sum it up quickly.
Hold up a finger on your left had, a couple of inches in front of your face. Now hold up a finger on your right hand at arms length. Line them up so one is covering the other. Now, keeping your hands still, move your head left or right. You will see that your fingers no longer line up.
Imagine the finger closest to your face was your reticle, and the further away finger was the target. When you moved your head side to side,  you changed your aim points and consequently missed the target.
This is parallax error and it will plague you from the moment you read this to the end of time. 
When you adjust the objective ring to the same distance as your target, it has the same effect as holding both your fingers next to eachother at arms length. Now if you move your head side to side, your fingers still line up. It doesn’t matter how much you move your head now, the aim point hasn’t changed and you should still hit your target. Parallax error has now been removed, and the pellet should go exactly where you are aiming.

As we know, you can’t change this setting once you have started a course. So you need to make a compromise. As a beginner it’s hard to know where this compromise is. So this adjustment is very useful for experimenting and figuring out your perfect set-up. Fixed objective scopes are available, but they are usually set to 100 yards. This is fairly useless for HFT where the maximum distance is 45 yards. Some of these can be adjusted, but don’t count on it unless you know what you are doing.
This adjustment is usually found on the front objective ring of the scope, and is twisted to adjust. However some scopes are ‘side focus’. These have the objective adjustment on the side of the scope and often have large side-wheels to make fine adjustments. This is very popular for FT where this adjustment is used for range finding, and therefore is useful to have within easy reach. This is largely useless for HFT though and not necessary for a beginner.

Summary
Well done if you’ve made it this far! Hopefully the information up to this point has been useful and cleared up some of the terminology that you will see when trying to pick a scope. One thing I haven’t mentioned is price. Sometimes this is the most important thing to consider. After all, most of us will have a budget of some kind.

For a beginner to HFT, I think £150 or less will get you a scope that does everything you need. The reason I think this is that my scope was £150 and so far, its been perfect for me. My personal best in HFT is 48, and at no point was the scope responsible for any of my misses (that I am aware of).
Even better than this, my girlfriends scope only cost £75 and her PB is 51.

If I was going to recommend a scope to a beginner, using the categories above,  it would be something like this:

  • Objective lens diameter = 32mm, 40mm, or 42mm
  • Reticle = Mil dot, or half mil dot
  • Eye relief = Any
  • Tube diameter = 1 inch
  • Focal plane = Second Focal Plane
  • Length = Any
  • Weight = Any
  • Lens quality and coating = Any
  • Ocular lens adjustment = Any
  • Magnification = 3-12 or 4-12
  • Elevation turret = N/A
  • Windage turret  = N/A
  • Reticle illumination = No
  • Parallax (objective) = Yes

If I was buying an HFT scope for myself or a beginner, with a budget of £150, I would be looking at the following (prices shown are approximate). Just to make it clear, these aren’t recommendations, because I haven’t had a chance to try them all! 

Hawke Vantage Max 4-12×40 AO 1/2 Mil Dot = £120
MTC HX 4-12×40 AI 1/2 Mil Dot = £130
Tasco Varmint 6-12×42 Mil Dot = £125
Hawke Vantage 3-12×40 AO Mil Dot = £90
BSA Essential 4-12×44 AO Mil Dot = £92

ATOM Optics 4-16×40 AO IR = £49.99 – See edit below

That’s the end of Part 1. It ended up being a bit longer than I had initially planned, but I felt that taking any detail out would defeat the object a bit.
Part 2 will be all about how to fit your scope to your gun, and then set it up properly. I’ll try to include lots of pictures and some step-by-step guides. 

 

*EDIT 19th September 2017*
I’ve got an update on scopes to look out for. I’ve been offered the chance to review a scope which might be perfect for newcomers to HFT. It’s the ‘In Your Sights’ ATOM Optics 4-16×40 AO IR (£49.99). I’ll reserve judgement until I’ve got it in my hands, but the spec looks very good for the price. Look out for a review in the near future.

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4 Comments on "HFT – Scopes Explained"

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Glenn Walsh
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Very good. Thank you for that.
Just a note. I shoot hft a steyr 110 . I’ve tried a few scope on top, but couldn’t quite settle with them 30mm tubes. Then I happened across,around hand a delta titanium. 4×14×44. 1 inch tube. Ftp. Wow.! Transformered my shooting. I think what you’ve explained about the exit pupil and parallax is the answer for me.i bought the scope for its aim points. Nothing else. Now I see what I got for free as a bonus.
The difference? Yes! Avg 45/50 now 50/ 55.

John Turness
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Dan, A really good article for the beginner, thanks. I have one question regarding the illuminated reticle. Is this a gimmick used to sell scopes or a useful tool? I ask this as HFT rules indicate no adjustment to your scope can be made once a competition has started.
The photographs in your article you are using a Hawke scope. Is this the Hawke Vantage Max 4-12×40 AO 1/2 Mil Dot ? If yes would you recommend this scope for a beginner ?