The term windage in ballistics represents a horizontal adjustment plane. Usually, adjustments can be made on scope turrets (in most cases, on the right side of the scope). Mounts that offer possibilities to adjust windage are rare and almost always more expensive than ordinary mounts.
In the first place, windage adjustments on mounts are made to compensate imperfections of the mounting surfaces/holes/platforms on the rifles.
These types of mounts are more common on hunting rifles and not so much on other sports, tactical or similar rifles, and they are usually made as a one or two-piece mount.
The basic principle is that the rings (or scope rail mounting elements) can rotate around their vertical axis. One ring has a fixed axis (usually front one) and the second one (usually rear one) can be moved left or right in the oval hole.
These types of windage adjustments have to be continuous and do not have to be bigger than expected errors on rifles. Such mounts are not used for windage corrections while shooting. We can correct only imperfections of different mounts while mounting the mount on the rifle.
It is important to know that they are usually made good enough not to flex the scope tube or create material tensions.
This Croatian manufacturer of scope mounts has two screws on the rear part of the mount that help to adjust windage (left / right adjustments).
By adjusting the rear end and having front end fixed, it is easy to make windage adjustments. All of their mounts for break-action rifles are one-piece mounts and in the contrary, all of their mounts for Steyr SSG, CZ 550, and CZ 527 are two-piece mounts.
All their mounts have in common that windage is adjustable by two screws on the rear part or end of the mount, which also includes all of their pivot mounts.
EAW mounts are known for fixed bases and the possibility of adjusting the ring in the base. It is interesting that they use this solution also on two-part mounts (separate base and rings) for Picatinny rails and dovetails for Sako rifles, which is rare.
The rear part of the mount (there are always two bases) has its hole in an oval shape which allows the user to move ring in it left or right, eventually adjusting windage.
Windage adjustment is also determined by how far away the bases are mounted. If bases are close together, there is eventually more windage adjustment allowed because of the wider angle (if the distance between bases is short). When bases are far away (one from the other), the angle in windage adjustment is eventually smaller and in this form windage adjustments are more limited.
It is also important to know that it is always the rear base that has an oval hole that allows windage adjustment and never the front one.
EAW also produces a whole bunch of one-piece scope mounts for break-action rifles and all their pivot mounts with windage adjustment are made with the same principle of functioning.
With Recknagel mounts, made from two parts (base and ring separated), the base has to be chosen according to each specific rifle manufacturer and model of the rifle. This means that they have a lot of different mounts, specific for each rifle and the customers can always choose (while placing an order) if they want windage adjustable mounts or not.
This is the main difference, compared to EAW, with which you cannot choose this option – EAW have all of their mounts windage adjustable.
Although, the prices of Recknagel mounts do not differ much if chosen with possibility of windage adjustments or not.
All of the mounts that enable rotation around their axis, are more or less known as pivot mounts.
EAW pivot mounts and Rusan pivot mounts have two screws in the rear base that allow windage adjustments. On the other hand, MAK and Recknagel mounts are made with different solutions – they have one part, named spacer, that allows rotation around its vertical axis and is eccentrical.
This spacer is in the rear part of the mount and it also allows achieving wanted height of the ring. If the spacer is being spinned, windage adjustment is constantly changing, depending of the position of the eccentrical part.
MAK mounts have a special triangular shaped slot on spacer and their mounts have to be disassembled to adjust windage (and this is done by moving the spacer).
On the contrary, Recknagel mounts have a round eccentric part on spacer which is enabled to rotate freely. When everything is adjusted, you only have to tighten the screw and voila – windage adjusted.
There is only one purpose of windage adjustable scope mounts – to correct imperfections of different parts on the rifle. Such mounts are normally more expensive than standard ones, which leads to special demand of finding specific customers. Not to forget to mention, windage adjustable scope mounts are in most cases made by European manufacturers. Thus, they are even less known in other parts of the world.
And something to think about – none of the manufacturers have made windage adjustable mounts with levels of adjustments yet. With all of the mounts it is the same – you have to adjust it with "feeling". There is no scale, no preset levels, no level controls or marks. Is this something that can be improved?