Setting Up a Telescopic Sight

Warning: - This set up guide will tell you how to correctly set up a telescopic sight. Always make sure you gun is safe and unloaded before working on it. Also, make sure you have permission to shoot on any land you use. If you go onto public land with a airgun, it is classed as armed trespass and this can carry a 5 year jail term.

Before we even start to look at setting up the scope, you will need to decide on the height of the mounts that you would like to use.

Most hunters, plinkers and HFT shooters want to keep their scope as close to the barrel as possible. This is because it makes the flight path of the pellet (as viewed through the scope) as flat as possible.

If the rifle you are using is a .177  with a power setting of 11.6ftlbs and a primary zero of 40 yards, If you set your scope height at 1 ½ from the centre of the barrel to the centre of the scope’s objective lens, your pellets will strike the targets between 16 and 34 yards (about ½ of a mil-dot above the cross hairs). At 45 yards, the pellets will hit the target ½  of a mil-dot below the cross hairs and the target at 8 yards will be hit just over 1 mil-dot below the cross hairs.

If, however, you have high mounts and set a scope height of 3”, then the pellet strikes between 20 and 40 yards will only be a ¼  of a mil-dot above the cross hairs, the 45 will be a ¼ below, but, the 8 yard target will be struck 4 ¼ mil dots below and even the 12 yard target will be 2 mil dots down.

So, if all of your shooting will be out beyond 20 yards, then high mounts may be the mounts for you, but before you spend your money, remember that the higher you set your scope above the barrel, the bigger the risk of inducing error by canting the rifle to the right and left. If you lean the rifle over even by a few degrees, by the time the pellet have flown 40 yards, it will miss the target by over an inch left or right depending on which way you cant the rifle.

I would personally recommend a good set of medium mounts and keeping the scope close to the barrel, but do remember that, if you rifle has a magazine, make sure there is enough clearance between the top of the mag and the scope.

Now that you have chosen your mounts here's how to set the scope up:

  1. Take the mounts and remove the top section (4 bolts each); keep these bolts safe. Once you have done this, place the mounts in front of you and place the scope on top of the mounts. There should be one mount in front and one mount behind the central turret of the scope and the central turret should point upwards at 90 ĚŠ. Make sure the mounting screws on the base of the mounts are pointing to the right hand side.
  2. Place the scope in the mounts, replace the top section and put the bolts back in. Finger tighten the bolts so that you can still move the mounts up and down the tube of the scope. (be careful not to scratch the scopes tube).
  3. After you have made sure the rifle is not loaded and that the safety is on, loosen the scope’s mounting bolts and offer the scope up to the rifle. There should be one mount in front of the loading tray and one behind. Place the mounts on the dovetail and finger tighten the mounting bolts onto the dovetail rail, but this time make sure the mounts can’t move.
  4. It is now time to set the eye relief. Get some old cushions or a gun rest and support the for-end of the rifle. Take the prone position and  (with the rifle in your shoulder), look through the scope at a target about 25 yards away. (set the parallax adjuster -  if your scope has one - for 25 yards and set the magnification to 10x), then, slide the scope back and forward within the mounts. You will see that when the scope is close to your eye, a thick black ring will appear around the edges of the sight picture. Push the scope forward until this ring just disappears, you now have the scope at the optimum distance from your eye and this is the scope’s eye relief. Once you have done this, tighten the mounts so that they very lightly grip the scope.
  5. Setting the fast focus at the ocular lens.( doing this will make sure that the cross hairs will be nice and crisp). Simply change the side or front parallax to maximum range, then point the scope at the sky (not the sun as this could cause blindness) and adjust the fast focus ring until the reticule comes into focus. Once the reticule is nice and sharp, use the scope’s locking ring (if it has one) to lock the fast focus in place. This is now set and it should never need to be touched again. You will now need to set up a plumb line and get a small bubble type spirit level, a cheap trick is to go to a pound shop and buy a builders’ spirit level, take it apart and you will now have 2 or 3 small spirit levels.
  6. Still using the cushions or gun rest  to support the for-end of the rifle, take the prone position and attach or balance the spirit level onto the scope rail (double sided sticky tape is good for this). Then, with the rifle in your shoulder, look through the scope at the plumb line, look at your spirit level on the rifle’s dove tail and make sure the bubble is between the two lines. Then look through the scope and make sure that the vertical crosshair is lined up perfectly with the plumb line. When it is, tighten up the screws, so that they hold the scope securely, but be careful not to over tighten, (a good rule of thumb is to tighten the screws enough to hold the scope so that it is just beyond finger tight and then give another quarter of a turn). If the vertical line of your scope cross hairs does not line up with the plumb line, you will have to loosen the top section of the mounts and rotate the scope to the left or the right. (be careful not to move the scope forward or backwards as this will affect the eye relief). Once the vertical line in the reticule matches the plumb line, tighten up the scope. Once you have completed this stage and the scope is nice and secure, double check your vertical crosshair is in perfect line with the plumb line and make sure that the spirit level is showing that the gun is level.
  7. To set the parallax, if your scope has a side or front parallax you just need to rotate the parallax adjuster on the side of your scope or at the objective lens.
  8. To set the parallax on a scope is quite straight forward; set a target at about 15 yards and one at about 45. Look at the targets through the scope and you will see that the one at 45 yards will be nice and clear, but the target close to you will be a blur. What you are looking for is a clear image on the 15 yard target as well as the 45 yards target. Set the adjustable parallax to about 25 yards and look at both targets, if the 45 yarder is clear, but the 15 yard target is still blurred wined the parallax adjuster towards the 20 yard point. You will see the 45 yards target start to blur. As it comes just off crisp, stop. You should now have a scope that is clear from 15  to 45 yards with a graduated amount of blur from 8 to 14. If your scope has a fixed parallax, (like the MTC Genesis and some Panoramas), the scope will already be set up; but, it is possible to adjust them, but this may invalidate your warranty, so please speak to the shop or the manufacture before attempting to adjust a fixed parallax scope.
  9. It is now time to set your scope’s zero and adjust the windage and elevation. The zero is split into two parts, which are the primary and secondary zero. Now, as I am sure you all know, unlike a rifle bullet, a sub 12ftlb airgun pellet does not fly in a straight line, it flies in a shallow arc on its way to the target. To explain primary and secondary zeroes, imagine a laser beam coming from your scope in a direct line to a target 45 yards away. As you fire the rifle, the pellet will leave the barrel (which is below the scope) and climb upwards through the laser beam, then, as it passes through the first time, this is your secondary zero It will then be above the beam for about 25 yards and as it drops back through the beam a second time, this is your primary zero. So the question is, what do you want your zero to be? A 40 yard zero has a secondary zero at 14 yards and every target from 15 to 33 yards is only ½ of a mil-dot above the crosshairs, the 45 yard aim point is only a ½ mill-dott below. So this means that every target from 15 to 45 yards, is covered by a single mil-dot spread, which is why I would recommend  40 yards to start with. It is now time to zero your rifle. (Try and do this on a calm day with no wind or rain), place a box or piece of paper with a pen mark in the middle at about 15 yards away (making sure you have an adequate backstop).  Fire a pellet at the mark you have made and see where the pellet has struck. If it is high and right, click the elevation down and the windage left, do this in 5 click increments and shoot again, and continue to do this until you are very close to shooting on top of the pen mark. Then move the target out to your primary zero distance (40 yards etc) and fire a shot into the centre of the target. Then fire 3 more shots at the first pellet mark and see where they land. If they all land left and low, then click the scope up and right and so on. By doing this you will be able to walk your shots in until you are able to shoot a 5 shot group, where all the pellets holes should be touching each other.
  10. Now that you have your primary and secondary zero, it is time to learn your scope, you can do this by placing targets in 5 yard increments, (10, 15,20, etc) and shooting each target. You will see that different ranges land on different aim points on your reticule. Write these down and you will now have a note of where to aim at what range.
  11. Shoot, shoot, shoot. The more time you spend with your gun and scope the better. Learn how hot or cold weather affect your scopes, if you can, shoot elevated targets and shoot as much as you can in the wind. If you do this, you will learn your scope in no time at all.
  12. Please, always shoot responsibly and if you need any help, we are always here to help.