Inside the body of every scope there is an erector tube that carries the reticle.
This is held in place by a return spring, and the turret adjusters.
When the scope is zeroed, the position of the reticle is altered by turning the turrets.
These push the erector tube up and down or from side to side, against the tension of the return spring.
If a turret is adjusted too far in a direction the erector tube will be pushed against the inside of the scope body. This will restrict its ability to move in the other direction.This will then make it impossible to zero the scope.
To correct this a scope needs packing. This is done on the mount to raise the scope depending on which way the scope will not align.
There are two types of Telescopic Scopes:
Fixed Air Rifle Scopes:
A fixed air rifle scope is set on one magnification and can not be adjusted. The numbers work as follows, on a 4 x 40 scope it means the object you see when looking through the scope is magnified 4 times more than looking at the objects just with the naked eye.Once a scope is zeroed in with a fixed scope then there is very little need to alter the scope but the disadvantage is that you can not magnify the image any more than the set amount of magnification the scope has. These scopes are ideal for shooting at shorter distances when the extra magnification is not really required, for example in a barn or building.
The number after the magnification refers to the diameter of the objective lens on a particular scope. To clarify a 4×40 scope has a 4 times magnification with a 40mm objective lens.
Variable Air Rifle Scopes.
A variable air rifle scope has a magnification that can be altered and the first two numbers give the variants of the size that can be seen through the objective lens and this is written 4-12x or 3-9x. This allows you to see at least 4 times magnification and allows the user to magnify up to 12 times and the second example starts at 3 times magnification and can be altered up to 9 times magnification. The last set of numbers refers to the size of the objective lens, i.e. 4-12×40 has a 40mm objective lens and a 3-9×50 has a 50mm objective lens. These type of scopes are ideal for longer distance shooting. A scope of this will require more frequent adjusting at different distances.
Mounting A Telescopic Scope.
All scopes need mounting to the gun and there are various ways this can be achieved. A one or two piece mount can be used. The mounts fit onto the rail of the rifle with the fixings supplied with the mount then the scope is placed in the mount cradle and the top part of the mount is placed over the tube of the scope and again fixed in place with the fixing screws supplied. A one piece mount gives a more secure fitting, especially on a recoiling rifle.
On a Pre-charged, Co2 or a junior rife then a two piece set of mounts is adequate. The height of a mount required is determined by the size of the objective lens. The scope needs mounting as near to the rifle as possible to give the best accuracy. It is usually a 50mm and above scope that will need the high mounts and a set of medium mounts in most cases is suitable for a 44mm objective lens or less. Telescopic scopes also come in two diameters, with a 1″ tube or a 30mm tube. It is important to get the correct size mounts to fit the scope of your choice but we are more than happy to advise you on this.
Some rifles do not have a standard 11mm rail, they can come with a Weaver rail, which is again a different fitting for the mount but both tube sizes of mounts are readily available for both types of fittings.
Once your scope is mounted it is time to Zero the scope to the gun.