Zeroing a gun scope sounds like an easy enough procedure, and it is, but there are few simple tricks that will make you an even more accurate shooter.
If you have read our guide on how to mount your telescopic sight to your airgun, then you are ready for zeroing. Pick a calm, dry day with no or very little wind if you can and, whether on the range or in the garden, ensure that you are shooting from a stable bench and have a safe backstop in place. A bench bag is also very handy for providing a stable support for your gun and have the correct screwdriver to hand if one is required for adjusting your scope turrets.
If you are using a zoom scope, begin by turning it down to the lower end of its magnification. Now fire a five-shot group of pellets at a target about 10 yards away. A group of five shots should enable you to work out what scope adjustments need to be made without confusion being caused by the occasional pulled or stray shot, and the close starting range means that shots shouldn’t be able to drift wildly off target if considerable adjustment is required.
Look at where the first group of pellets struck the target to work out the necessary adjustment. If they landed low and to the left, you’ll need to adjust your sight up and to the right. On most telescopic sights, this is done by unscrewing the caps from the windage and elevation turrets to reveal the adjustment dials or by pulling the turrets out to unlock them.
The top (elevation) turret usually has an arrow marked ‘U’ showing you which way to turn it to move the point of impact upwards. The side (windage) turret usually has an arrow marked ‘R’ to indicate the direction to twist it if you want to move the point of impact to the right. Unsurprisingly, turning in the opposite direction with shift your shots in the opposite direction too.
Different riflescopes have windage and elevation adjustment dials with different scales of adjustment. With turrets marked ¼ MOA, one click will move the point of impact one quarter of an inch at 100 yards, which equates to four clicks for a shift of a quarter of an inch at 25 yards. Similarly, if turrets are marked ⅛ MOA, one click will move the point of impact one eighth of an inch at 100 yards and four clicks will cause a shift of just one eighth of an inch at 25 yards. The number-crunching can get confusing so the easiest thing to do when zeroing (at whatever range) is to try half a dozen clicks and shoot another group to see what difference it makes – you can then base further adjustments on this benchmark.
When zeroing, I usually start by adjusting just the windage dial, until I have the group aligned either above or below the target. With that sorted, I then move on to the elevation. Tackling the two different planes one at a time helps to avoid confusion and I’d usually hope to have found my 10-yard zero after shooting four or five groups. With that sorted, it’s time to move the target out to 15 yards - a distance which is also likely to correspond with point of impact at around 30 yards when using a sub-12 ft/lb airgun.
After achieving zero at 15 yards, move the target back to where you want to set your specific zero – 30 yards is usually a good rule of thumb for a sub-12 ft/lb airgun – and wind up the magnification to the level you expect to use most.
Zero shouldn’t be far off to start with, and a few shots should soon have you bang on target. When you’re satisfied that your scope is properly zeroed, screw the caps back onto the dials – or push the turrets back down to the locked position – to prevent any accidental shift. Now you can experiment over various ranges to work out the necessary aim off (hold-over and hold-under) needed to hit the mark at different distances.
Generally speaking, you can expect pellets to strike low at ten yards because they left the barrel a couple of inches below to line of sight. At 12 to 15 yards, the pellet will have risen to coincide with the crosshairs at primary zero, at 20 yards the pellet will have risen just above the line of sight and will strike a fraction high. Depending on your chosen zero range, the crosshairs will correspond exactly with the point of impact you dialled-in at say 30 yards and beyond that it will fall ever lower until it runs out of steam.
Practising on paper in this way will give you a very good idea of how your gun/scope/pellet combination performs but don’t forget that you’re unlikely to get a comfortable bench to rest on when you’re out hunting. Therefore, it’s equally important to shoot paper targets using the stances you would expect to adopt in the field. That way you’ll be properly prepared when you come to tackle live quarry.
