HFT – Scope Set Up

Welcome to part 2 of 3 of my beginners guide to scopes for HFT. Firstly I would like to say this post has been very kindly sponsored by the team at ‘In Your Sights’. They supply a range of shooting accessories and scopes, and have agreed to give you all a massive 10% off anything on their website. At the bottom of the post you will find another link to their site, and a promotional code.

Part 2 of this series is all about how to set the scope up on the gun, and some pit-falls to watch out for. You can use as little or as much of the information as you need. Some of it may be too much detail for garden plinking, but hopefully all of it will be interesting.

If you haven’t seen Part 1 of this mini series, please check out the link below. There’s a lot of information in there that may be useful if you are new to shooting or scopes.

Part 1

I have split this post up into the different stages I would go through to set up a scope, in the order that I would do them. This is probably a good place to say, none of these techniques are new, or invented by myself. If you search the internet you will find all of these, plus many more methods.
As with Part 1, the intention for this post is to be a guide for beginners. Therefore I will try to explain some of the jargon and technical side of things, as well as walking you through the steps.

Mechanical and Optical Centering – Theory
This needs a bit of explanation as to how a scope actually works. Inside your scope is a tube which is suspended inside the main body. This is called the erector tube and it has a several jobs. These are:

  • Holds two lenses which work together to magnify the image you are seeing. Turning the magnification ring at the back of the scope changes the position of these lenses. Moving them forward and closer together increases the magnification. Moving them backwards and further apart decreases it again
  • Holds the reticle cell. This is the piece of glass on which the reticle is etched. Remember in Part 1 of the blog when I talked about first and second focal plane? A first focal plane scope has the reticle at the front of the erector tube. A second focal plane scope has the reticle at the rear of the erector tube
  • Allows windage and elevation adjustment. The turrets for these adjustments are essentially screws which butt up to the erector tube. On the other side is a spring which resists these screws and holds everything in place. So adjusting these moves the erector tube in relation to the main body. 

    Erector tube inside the main scope body

Now imagine the erector tube is perfectly central inside the main body. This is an optically centered scope. The benefit of this is that technically, this gives the best clarity and optical performance. However to get the real benefit of this, you will need adjustable scope mounts, which I will explain later on. For this reason, I would recommend this as a more advanced set-up. And to be honest, it’s not something I do that often.

Optically centred scope on the left. Un-centred scope on the right

Mechanically centering a scope is simpler but with different results. The benefit of this is that you end up with equal windage and elevation adjustments in every direction. This minimises the chance of running out of adjustment. This doesn’t require special mounts, so is what I usually do. Depending on the design of the springs and turrets, this is likely to be slightly different to optically centering.

Mechanical Centering Method
This is fairly simple to do, but there is one thing to be careful of to avoid any damage to the scope. When you reach the end of the adjustment, the turrets will get stiffer to move. Stop as soon as this happens. You only want to count the ‘easy’ clicks.

Elevation fully in
Elevation fully out
  • Try adjusting both turrets a few clicks either way, just to make sure you aren’t already at the end of your adjustment. You want to start with them roughly in the middle
  • Now take one (doesn’t matter if you do elevation or windage first), and wind it all the way in one direction until it starts to get stiff. Now wind it all the way in the opposite direction, but this time count how many clicks of adjustment there are. 
  • Divide that number by two, then turn it back that many times
  • Repeat with above with the other turret

You should now have equal adjustment available in all directions. 

Optical Centering Method
There are a few different methods if you search for them, but this is the one I use. What we are trying to achieve is to rotate the scope around 360 degrees, and have the centre of the crosshairs looking at the same point the whole way round.
You don’t need to achieve perfection in the next steps. In fact it’s very difficult to get it completely centered. You just need to get somewhere close.

I prefer to do this when the scope isn’t mounted to the gun. Turning it round whilst it’s in the mounts can damage the paint, and there’s no additional benefit. If you have a set of engineering V blocks, these could be ideal. But actually all you really need is a cardboard box. It needs to be set up like so, with a pair of ‘V’ shaped cuts to sit the scope in:

Cut the box like this
The scope sits like this

The cardboard is nice and soft, so won’t damage the finish on your brand new scope, and this method is accurate enough to get the result we are after. What you need to do now is:

  • With the scope set in the grooves, look through it and aim it at a clear target. This can be anything really, as long as you can see it clearly
  • Still looking through the scope, rotate it 360 degrees and watch the centre of the crosshairs. You should see that it moves in a circle and then comes back to where you originally pointed it
  • Try to picture where the centre of that circle was. With the scope back at the starting point, adjust the elevation and windage to move the crosshairs in that direction
  • Each time you do this, the circle that the crosshairs makes will get smaller. Eventually you will end up with a small circle and it will be difficult to get any more improvement. This is when you know you are done.

I’ve taken some photos showing every 90 degrees rotation. On the first picture I have shown each of the aim points (green circles) and the rough centre (pink diamond). In this case I would need to move my elevation down, and windage to the right slightly. Then repeat the process.

Scope upright, aim points, and estimated centre
90 degrees
180 degrees
270 degrees

Attaching mounts to the gun
The next step is to install the scope mounts to the gun. This is relatively simple with only a couple of things to look out for.
There are a few different types of mount available. I think the most popular will fall under either; single piece, double piece, and adjustable. They also come in different heights for different sized scopes. Check with your shop that you are getting the correct height. They will be able to check for you and advise you on the most suitable.

Single piece mounts have two rings and caps, but they both share the same base. 
Pros: Provide more surface area for clamping to the gun. This can be useful for springers with a lot of recoil, as it will minimise the chance of the scope moving.
Cons: Can get in the way of loading ports or magazines, especially on PCP’s. They also don’t allow both rings to be mounted in front of the turrets. This can be a problem for scopes with low eye relief, or older guns with short scope rails.

Single piece mount

Two piece mounts are two rings that are completely separate from each other
Pro’s: More flexible mounting arrangements possible. Allow clearance for PCP magazines. Generally cheaper
Con’s: Less clamping surface area (although not really a disadvantage for most guns)

Two piece mounts

Adjustable mounts can be either single or double piece. But they differ in that they allow windage adjustment. Some also allow elevation adjustment.
Pros: Allow additional adjustments and proper optical centering to be used. 
Cons: More expensive

Once you have chosen which mounts you will be using, look at the underside. You should see that one of the mounts (or one end of a single piece) will have a pin recessed into it. This is a ‘recoil stop’ pin and is used for spring or gas ram rifles. This is designed to stop the scope shuffling backwards on the rails due to recoil. If you look on the scope rail of your springer/gas ram there should be one or more holes for this pin to sit in. Some older guns won’t have these holes, and they aren’t always needed with good quality mounts.

Scope recoil pin
Recoil stop holes in rail

Undo the base of the mount and slide it onto the rail. Line up the scope pin to the rail hole, and then screw it in, usually from the top. This needs to be done before the scope goes on! I always put a bit of blue loctite on this screw because I have had one wind itself back up into the mount once! If you are using a PCP, make sure this pin is hidden inside the mount as you won’t be needing it. If you are using the pin, this mount can no longer be moved.
Slide the other mount onto the rail and nip the screws up. Not too tight at this point. Make sure that the base screws are all on the same side of the gun. This will help with the scope alignment.

That’s the mounts attached to the gun. Next the eye relief needs to be checked, which may determine the final location of the front mount of a springer, or both mounts on a PCP.

Eye Relief
As I mentioned in Part 1, eye relief is the ideal distance between your eye and the rear lens of the scope. To check this, the scope needs to be placed in the mounts. (The elevation turret always points up, the windage turret always points to the right). At this point I lightly screw on the top caps. They should be loose enough to allow the scope to move back and forth, and spin round. It should be easy to move the scope into a fully forward or fully backward position.

Scope forward
Scope backward

You will need to find a nice clear object to look at, the distance doesn’t really matter as we will be concentrating on the edges of your view. Shoulder the gun and look through the scope. If edge of your view is blurry all the way around, the scope needs to move closer to you. If there is a crescent of blurriness, it needs to move away from you. Adjust the scope until the image is perfectly clear at the edges.

Too close to eye,  image reduced  in bottom left edge
Too far away from eye, image slightly blurry all the way around
Just right. Edges of the images are crisp and clear

The most important thing to remember here is that you should be adjusting the scope to suit your head position, so be careful to keep your head in the correct place. The trick I use is to close my eyes and get in my shooting position. Then I open my eyes and check for blurriness. Every time I  make an adjustment, I close my eyes and repeat the process.
Some older air rifles (particularly certain BSA’s….) were not originally designed to have scopes. So the rails are very far forward. To get correct eye relief, both mounts might have to sit in front of the turrets. 

One of my BSA Airsporters with very short scope rails

Now you have a good idea of where the scope will sit, you can set the position of the mounts. If you are using a springer with a single piece mount, you will find you have very little control over this. It is what it is! However with separate mounts you can adjust them a bit. I like to get the mounts as far away from each other as I can. This will minimise the effect of misalignment, which may be small, but is worth thinking about. 

Now go ahead and tighten the base of the mounts. The position of these is now set. If possible, use a torque screwdriver, or a small torque wrench to tighten the screws up to the manufacturers recommendation. Over tightening these base screws won’t cause any real problems. But you might cut into the material, or round the screws out which never looks good, and makes them harder to get off again.

Proper tools are worth having for set up and general maintenance

If you don’t have access to these tools, using allen keys is ok. I generally use the long arm for leverage, and only go as tight as I can with one finger.
Now double check your eye relief, and then mark the position on the scope. I use either a soft pencil, or a piece of tape, to mark just behind the rear scope ring. This way, whatever other changes you need to make, you can always get eye relief in the right place.

Ocular lens adjustment
The ocular lens adjustment is the rearmost (closest to your eye) and is usually a ring that turns. This setting will be different for everyone, and will be the main reason that looking through other peoples scopes is awkward.
What we are trying to achieve is to have the reticle as clear as possible. The easiest way is to set the parallax adjustment (if you have this) to infinity and look through the scope at a bright blue sky. Please don’t look into the sun while you are doing this! If you don’t have bright blue sky handy, a white wall will do as long as it is brightly lit.
Now turn the ocular lens adjustment until the reticle is crystal clear. Some scopes will have just a ring to turn, others will have a locking ring. So look for this if its a bit stiff!

Locking ring on the bottom scope, just where the tube narrows

Unfortunately your eye will try to help you out by focusing on the reticle and making it appear very clear. So what you will need to do is look somewhere else for a few seconds to re-focus your eye. Now quickly look back through the scope and see if the reticle is still clear. Essentially you are trying to surprise your eye and not give it time to react and adjust.
Once this is done, you wont need to touch it again (unless maybe your glasses prescription changes). Sometimes I even tape it up in case someone unwittingly plays with it…

Objective Bell Adjustment (Parallax)
I will cover this in more detail in Part 3. For now though, try to ensure this is set to roughly the same distance you will be shooting at. This will make the targets and your reticle clearer, and generally make the next steps easier. Just turn the ring at the front of the scope until the desired distance marker lines up with the static mark. If your scope doesn’t have this adjustment that’s ok. This will be fine for most plinking and range shooting. But for HFT it’s not ideal, as I’ll explain in Part 3 next week. 

Adjustable objective ring

Windage & Elevation. Stage 1
This is the first stage of setting windage and elevation. You can ignore this step, but it will undo some of the work you did earlier with the optical or mechanical centering. For general plinking, I would only come back to this stage if I ran out of elevation or windage adjustment later on.

If you just screw some mounts and a scope to your gun, there are several variables that can affect the end result. The scope rail has to be machined onto the main action of your gun. Any kind of machining will be slightly off, even if its a tiny error. Then the mounts are attached. These have two possible errors. In the base, and the rings. Then the scope goes on top, and this may not be perfectly straight either.
Occasionally these errors will add together and the crosshairs will be a long way off centre. This means you will have to use lots of windage and elevation adjustment to correct it. Therefore you will no longer be optically or mechanically centered, and will lose the benefits I wrote about earlier.

To test how far off you are, first you need to tighten up the scope caps. Over tightening these is much worse than the base screws. You could damage the body of the scope, and even the erector tube inside. I’ve seen scopes that were so tight, the magnification stopped working.
If you don’t have a torque screwdriver or torque wrench, use an allen key. But this time use the short leg for leverage, and only do the screws up as tight as you can with two fingers. It’s also worth going round and doing each screw half a turn at a time. This helps keep the pressure even across the caps.
Try to get the reticle roughly lined up by looking at a straight edge (e.g a door or window frame) before you tighten everything down. It does’t have to be perfect at this stage. We will sort this out soon.

Set up a large target at approximately 10 or 15 yards, making sure you have a good back-stop. Draw a target to aim at and take a couple of shots, always aiming at the centre of the target. Hopefully the pellets will go in roughly the same place, wherever that might be. If they didn’t hit the target at all, either use a larger target, or bring it closer until you can see where the pellet impacts.
My rule here is that if the pellets are within a 3 or 4 inch inch circle, I’ll move onto the reticle alignment. If they are outside this circle, I will make some corrections first. If the target target below was 5 inches across, the green circled examples I would be happy with. The red circled examples I would want to correct.

Red examples I would address if possible

If you have fully adjustable mounts, this is easy. Follow the instructions from the manufacturer and adjust the windage and elevation on the mounts only. Once you are happy with where the pellets are landing, move onto the next stage.

If you have more basic mounts, its a bit more complicated. If the windage (i.e the left and right) needs adjustment you can try turning the scope mounts around so the screws are facing the other way. Or swap the mounts back to front if you aren’t using the recoil pin. However if this doesn’t make enough difference, there isn’t much more that can be done.
If you are using a single piece mount with the recoil pin, you are also a bit stuck. If you are in this position but you want an optically centered scope, the only real choice is to buy adjustable mounts.

If the elevation needs adjustment, you can use shims. The most common material to use here is old film negative or aluminium drink cans, cut to size to fit into the bottom half of the scope ring. If you need to bring the pellet down, put a shim in the rear mount. If you need to raise the pellet up, put the shim in the front mount. If you are using film negative, I would use a maximum or 3 or 4 shims. With the aluminium drink cans I would use just one or two shims. Any more than this and you risk having too much angle, and damaging the scope. If you aren’t confident trying this, please don’t. Adjustable mounts will always be a better option.

Shim location in lower part of the mounts

If you have tried swapping mounts around and shimming the scope but your pellets are still landing a long way from centre. I would consider asking for advice from a trusted friend, member of a club, or gunsmith. You might have other problems, such as bad mounts or even worse a bent barrel.

Windage and Elevation. Stage 2
This will explain how to set your windage and elevation, to give you a ‘zero’. What this means is that at a given range, the pellet should land exactly where the middle of the scope is looking. i.e you make zero adjustments to your aim point.
Firstly we have to pick a range to zero at. This will be discussed more in part 3 next week, but for now lets use 20 yards. I like to set out two targets at this range and adjust elevation and windage separately. The first target has a thick horizontal line in the middle and is used for elevation. This is always the turret at the top of the scope. Have 3 shots at the target, and they will hit somewhere above or below this line. 

  • Pellets land above the line = Adjust the turret in the down direction (usually turning clockwise)
  • Pellets land below the line = Adjust the turret in the  up direction (usually turning anti-clockwise)

To start with, try using 5 clicks of adjustment at a time, then have another group of shots. As you get more experienced, you will get a better idea of how much adjustment is needed. Once you are closer to the line, use less clicks for each group of shots. The reason I use 3 shots is to make sure they are all landing in the same place. If the gun is shooting pellets randomly at the target, zeroing will be impossible. This could be a sign of poor quality pellets, loose screws or a broken scope.

The procedure for windage is the same as before, except now you want to use a target with a vertical line. This turret will be on the right side of the scope.

  • Pellets land to the left of the line = Adjust the turret in the right direction (usually anti-clockwise)
  • Pellets land to the right of the line = Adjust the turret in the left direction (usually clockwise)

This procedure is relatively simple but can become frustrating, especially for beginners to the sport. There are many factors that can affect the accuracy of the set-up, and therefore where the pellet lands. A combination of poor quality rifle and pellets may struggle to put the pellets in the same place every time. Especially if being used by a new shooter with a poorly adjusted trigger for example. However this is not a problem. You just need to have realistic expectations of how the set-up will perform. The best advice I can give is to go to a local range, where there will always be someone willing to give advice, or help you with your zero.

Reticle Alignment
The aim of this step is to get the vertical axis of the reticle to be perfectly vertical, and likewise the horizontal axis to be perfectly horizontal. This means that when you use holdover, or adjust for windage, it will be predictable. If the scope is canted over to one side, shooting with holdover will also act as if ther is wind blowing the pellet. So your shot won’t go where you are expecting.
Technically the scope can be level in any position, depending on how the gun is held or canted over, so actually we need to adjust the scope in relation to the gun itself. This means The vertical axis of the reticle will be perfectly in line with the barrel of the gun. It’s then your job to stop the gun from canting.

There are a couple of methods I have tried. Although everyone will have their own preference. All methods will need the scope free to rotate, so loosen off those scope caps.

Using a bubble level: 
This method involves the use of a bubble level and a plumb line. The bubble level is the same as you would find on a builders spirit level, except this one has a scope rail fitting. Fit the bubble level, then hang the plumb line up with a good weight at the bottom to keep it tight. With the gun perfectly level, look through the scope at the line. Now rotate the scope so the verticle crosshair is parallel to your plumb line. 

Bubble level fixed to the scope rail

Using a Mirror:
This needs good light, a mirror and a helper. Holding the gun as steady as you can (a rest helps). Look through the scope into the mirror. You need to be as straight on to the mirror as possible for this to work, hence the helper who can adjust it for you. If you line up the crosshairs with the centre of the reflected scope, the centre of the barrel should be bang on the vertical crosshair. This method is only a quick check and will not be as accurate as using a bubble level and a plumb line.

Test Shots
You can also test this alignment by shooting groups of pellets at different distances. If you draw a perfectly vertical line on a target, then shoot it at different ranges, all the pellets should land somewhere on that line. However this assumes there is no wind, and you are a very good shot with good trigger technique. Again this is a quick check and not as accurate as the bubble level.

Scope axis to bore axis alignment
This is my least favourite part of setting up a scope, because it is the hardest to check and rectify. The potential problem we are looking for, is if the scope and the barrel are not pointed in exactly the same direction. See exaggerated picture below. In this example, if you zero the gun for 25 yards, at 10 yards the pellets will land to the left of your aim point. Then at 45 yards, the pellets will land to the right of your aim point. 

Exaggerated example of bore misalignment
Effect of bore misalignment

However there is some good news. This error is only likely to be very small. I have never had it be a big problem. 
To test for this misalignment, first zero your scope to 20 yards. Now shoot a target at 10 yards, and another at 30 yards.  Aim for the bulls eye each time and don’t adjust the scope between shots. This method does require that you are a good shot, or someone who is a good shot could help you if you aren’t confident.

In reality the worst I have seen was with a cheap scope and cheap mounts. The 10 and 30 yard pellets were almost touching the vertical line, and I had to do a lot of attempts to prove it wasn’t my bad technique. In this case I fixed the issue by turning the scope round slightly in the mounts. The scope alignment was now slightly out, but not enough to make a real difference to my shooting. At air rifle ranges, this is unlikely to be a real problem. However I am always happy to be proven wrong, so leave me a message if you’ve had a bad alignment problem, and let us know how you fixed it.

And that’s it! You may be pleased to know that this is the end of Part 2. I know it was an even longer read than Part 1, but thank you for sticking with it. If there are any beginners reading this, I would love to hear from you. Was this article helpful? How could I improve it in the future? Let me know in the comments, by email, or on Facebook.

Part 3 will be more specific to HFT and will discuss different methods of zeroing and range finding.

As I said I said at the start of this post, I am very pleased to say this post was sponsored by ‘In Your Sights’. They are a UK based company selling a range of shooting accessories, including scopes and mounts and they are offering a huge 10% discount on everything on their website. Simply add the following code to your order at the checkout:

www.inyoursights.co.uk

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