In recent years we can observe that a trend of Picatinny rail has become widespread and global. It is driven by the NATO standardized rails, more commonly known as the Picatinny rail standard. Picatinny rail being the New Jersey Arsenal that developed it in 1995.
These mounting options are revolutionary. The biggest and best advantage being that the Picatinny rail can be used its entire length and not bordered to a few pre-designed slots like for example the Weaver rail standard was before.
The other main advantage is the ease of use and interchangeability. If a product is meant for a Picatinny rail design it will fit all Picatinny-rails, no matter the manufacturer or date of production.
Picatinny Rail and Weaver rail profile
The Picatinny rail is almost exclusively crafted from a single piece of metal (in some cases aluminum). In this manner, the axis of the Picatinny rail is perfectly straight and aligned with the axis of the firearm. Therefore the rifle scope which is mounted onto this kind of configuration is certainly aligned with the rifle / gun and the trajectory of the ammunition.
Weaver rail design on the other hand is usually manufactured in two separate pieces, greatly increasing the possibilities for the axis to be crooked, overlapping, and out of line.
It is always harder to align two separate pieces to a third line than it is to align one piece to another. In this way, the lapping of two mounting rings on a single-piece Picatinny rail is no longer required.
The single-piece rail will assure that both rings are perfectly aligned to each other and that no unwished stress is transferred to the riflescope.
The Picatinny rail itself is an evolutionary step forward from the older Weaver rail. The main difference between Picatinny rail and Weaver rail is the spacing of the slots. Picatinny rail design has them evenly placed exactly 5.23 mm from one slot to the other, 3 mm deep. For this reason, the mounting options are repeatable and the same as other firearms using the Picatinny rail standard.
Interchangeability was a major driving force in the development of the new standard as different NATO armies need to be compatible with each other.
Weaver rail has 3.8mm wide slots and these slots can be placed anywhere on the Weaver rail and in any number that the producer wished.
A big advantage for using the Picatinny rail design is the ever-present recoil stop. Furthermore, the manufacturing of the rail is not very technically demanding and can be done without the use of state-of-the-art machines which greatly reduces the cost of the finished product, making it very affordable.
The Picatinny rail is easy to mount and usually, this type of configuration does not transfer negative stresses and forces from the fired weapon to the rifle scope.
In addition, the Picatinny rail with its very long useable surface works well for mounting longer rifle scopes or to achieve optimum eye relief.
The durability and toughness are other big pluses for this solution.
A majority of the Picatinny rings are fixed, but a number of best rated European manufacturers (EAW, MAK,..) have, in recent years, put a lot of effort into the development of detachable ring with100% repeatability, with which it becomes easy to remove the scope from the weapon without the use of tools.
No re-zeroing is needed with such mount options, but these models tend to be expensive.
Picatinny rail and weaver rail share one more thing. It is possible to use the Weaver ring and the Picatinny ring on the Picatinny-rails, but it is usually impossible to use the Picatinny ring on the Weaver base. The reason being the above-mentioned positioning and spacing of the slots.