Target Sports

SCOPE MOUNTING GUIDE: ALL SCOPED UP PART TWO

Created on 14th May 2009

Here's MARK CAMOCCIO with a basic guide to zeroing the scope

THE TERM ‘zeroing' means to set the scope up so that the impact point of the projectile falls directly behind the main intersection of the scope's cross-hair or reticle. In other words: what you aim at, you hit! Having spent my whole life shooting airguns of one sort or another, it's fair to say I'm a dab hand at zeroing - I pride myself on getting pretty close to the target within four to five shots. Cocky? Well yes, of course - but as in any task, experience plays a huge part. I appreciate that it can all seem rather daunting for newcomers to our sport as they will most likely be totally unfamiliar with the equipment. Certain rules apply, and when problems arise a methodical approach is the order of the day. If you read part one in last month's issue (Target Sports August p.28), you will have reached the point where the scope is now firmly in place on the rifle and so zeroing can begin.

Distance

An important decision has to be made with regard to the distance at which the rifle is to be initially zeroed. I seem to be locked into a 35yd zero, which probably stems from my FT grounding. Indeed, 35yd is as good as any for this demanding discipline, although it's largely academic since the target ranges are usually simply dialled into the scope turrets. For hunting or general-purpose airgun shooting 30yd is a good choice, helping to keep the trajectory reasonably flat. Pellet weights and calibre can all dictate the selection, but 30yd is popular and represents a good compromise. Targets that arise nearer, or further away, may need some adjustment - but everything stems from an initial accurate zero.

Position

A stable shooting position needs to be adopted in order to achieve a valid zero. It's worth noting that a recoiling rifle, such as a spring-powered model, may well show a different impact point depending upon the position adopted. The rifle may be spot-on from a kneeling position yet shoot ½" high from the over-arm FT pose. It therefore makes sense to zero the scope using the position from which most shots are likely to be taken. The recoilless action of a PCP is far more forgiving and should hold an identical impact point, regardless of a change in shooting stance. For the PCP, zeroing from a bench rest such as the Deben Pro-Bench can be beneficial. Lying prone and bedding the rifle into a beanbag or cushion can be just as stable, though. Remember that the exercise is to fine-set the scope, so all variables, including a suspect shooting technique, ideally need to be removed from the equation. Recoiling rifles should not be allowed to touch a hard surface on firing, so a supportive grip - placing the hand between the rifle and any hard support, such as a tree or post - is the ideal.

Backstop

As always safety should be borne in mind, and ensuring that a solid backstop is in place has to be top of the list. I still use the time-honoured funnel-shaped metal pellet-catcher box, but being around 8" square this still requires the rifle to be only a few inches off zero, and so is too small for this general exercise. Bear in mind that a new scope as just mounted onto a rifle can be a foot or so off-target at 30yd, so it's obvious that a large screen is needed. I have a 4ft by 3ft steel sheet as an absolute safety screen, and in front of this I place some carpet, with a target card held in place with bulldog clips.

It can be frustrating when frantically trying to see where shots are falling, so intricate printed targets are unwanted here. Keep it simple and just take a large white sheet of paper or card, around 2ft sq, and, using a bold marker pen, draw a couple of small dots or circles in the centre, around ½" in diameter.

Adjustments

The turrets on most scopes come with ¼" adjustments, that is to say each click represents a change in the point of impact (POI) of ¼" at 100yd. It therefore follows that four clicks equals ¼" at a more relevant 25yd and 16 clicks will change the POI by 1" at the same range. For the purposes of speed-dialling, 16 clicks is normally equal to around ¼ revolution of the scope turret, so quick adjustments can be made when necessary. Many scopes now come with ¹/8" adjustments, so the above guide will vary accordingly.

If the scope has enclosed turrets, unscrew and remove the caps, putting them somewhere safe, and take a look at the mechanism. Older designs (including most of my scopes) require a coin or screwdriver to locate in the slot and turn the turrets. Many more modern designs either have raised finger bars, which are easily turned, or push/pull turrets which, having no covers, are simply pulled to unlock the mechanism; then the entire turret is rotated. While this latter design is certainly user-friendly, it is more prone to the zero being accidentally knocked or misaligned in the gun case, for example.

To the range

In order to catch the shots easily (in case the scope is way off its setting for any reason), start the shooting session from a really close range - around 10yd - and, taking time to carefully aim, take two initial shots. Irrespective of the turret-type, there should be a marked arrow saying ‘up' or ‘down'. If those initial shots at 10yd have gone 3" high, for example, then you can do an exact proportional calculation on the number of clicks required - or just speed-dial in a couple of complete revolutions on the turret and gauge the effect. The turret arrows are showing the direction to alter the point of impact, i.e. in our example we want to lower the point of impact, so the turret would be turned towards the direction of the ‘down' arrow.

Once the shots are within an inch or so, move the target back to a distance of 25yd. Then the speed-dialling process can be performed with confidence - so if the shots are still hitting 2" up and 1" to the left then the turret can be turned half a revolution ‘down', and ¼ of a turn to the right.

Two golden rules exist regarding zeroing. The first of these is: do not ‘chase the shots'. Always aim spot-on, regardless of where the shots fall. Secondly, once fine-tuning of the zero is being attempted base any adjustments on five-shot groups: anything less isn't necessarily representative. Once the zero is satisfactory, again, depending upon the turrets, the zero point can be marked. Some turrets have provision to remove the top cap with an Allen key and reset at point ‘0' on the scale; thus, when the turret is clicked to ‘0' hereafter, it is set to the zero range. Other scopes may have a rotating bezel (an outer movable ring), which is simply turned using a screwdriver; this too indicates point-zero.

Now, in an ideal world, follow-up shots would all be spot-on and we'd all live happily ever after. OK; life's not always that kind to us, and some strange happenings can take place.

In the final article on fitting a scope to an air rifle, I'll touch on some problems that can arise, and what can be done to remedy the situation.

SCOPE MOUNTING GUIDE: ALL SCOPED UP PART TWO

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SCOPE MOUNTING GUIDE: ALL SCOPED UP PART TWO

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