Scope mount


Scope mounts are rigid implements used to attach a telescopic sight or other types of optical sights onto a firearm. The mount can be made integral to the scope body or, more commonly, an external fitting that clamp onto the scope tube via screw-tightened rings. The scope and mount are then fastened onto compatible interfaces on the weapon. Words such as mounts and bases are used somewhat loosely, and can refer to several different parts which are either used together or in place of each other as ways to mount optical sights to firearms.
Attachment interfaces for scope mounts vary according to weapon design and user choice. Traditionally scope mounts are fastened onto firearms via tapped screw holes and/or clamps. Since the mid-20th century, dovetail rails, where the mount is slid over a straight dovetail bracket with an inverted isosceles trapezoid cross-section and fixed tight in position with clamping screws, became more common due to the ease of installation and removal. Later, the hexagonally cross-sectioned rail interface systems such as Weaver rail became popular and was later modified into the Picatinny rail in the early 1990s, which became the standardized military-use mounting interface for NATO troops in 1995. The Picatinny rail was officially replaced by the metrified NATO Accessory Rail for military use in 2009, although it remained popular in the civilian market for both scope and accessory mounting.
Scope mounts can be either one-piece or multi-piece. These mounts are usually fastened with screws to specified tensions, but sometimes they are manually tightened via thumbscrews, and may even have Quick Release designs. As of 2020, the Picatinny rail is arguably the most widespread scope mounting standard for new firearms, although there are many proprietary and brand-specific types of mounts that can either be used with Picatinny rails, or as completely different design alternatives. Scope mounts may be offered by firearm and scope manufacturers, or bought as aftermarket accessories.

Integral scope mounts

Zeiss rail

Among scopes for rail mounts, the 22.5-degree V-shaped Zeiss rail is the most prevalent standard. It was introduced in 1990. After the patent expired in 2008, compatible scopes have been offered from manufacturers such as Blaser, Leica, Minox, Meopta, Nikon, Noblex, Schmidt & Bender and Steiner. It has therefore, in some sense, become the de facto industry standard for scope mounting rails. The system has so far seen most use on the European high end market.

Swarovski SR rail

The Swarovski SR rail has a flat rail with many "teeth" as recoil lugs, and is only offered on scopes from Swarovski and its subsidiary Kahles. It separates itself from the Zeiss rail in that it is not neither stepless nor self-centering.

S&B Convex rail

A former competing standard was the halv-circle shaped Schmidt & Bender Convex rail also introduced in 2005. Schmidt & Bender after a few years changed to the Zeiss rail standard. In contrast to the Zeiss and Swarovski systems, the S&B Convex rail had the possibility to add a cant to the scope when mounting, such that the reticle is not horizontal to the ground.

70-degree prism rail

There is an older European system with an upside-down V-shape. This system has little widespread use today. The advantage of this system was that it at one time was offered by most European scope manufacturers, but the disadvantage was that the rail had to be drilled for a screw each time the eye relief was to be adjusted. All new standards for rail mounts have addressed this issue.

Ring mounts

Ring mounts usually consist of a base attached to the firearm and rings attached to the sight. The rings are usually made of steel or aluminum. Common diameters on ring mounts are 25.4 mm, 26 mm, 30 mm and 34 mm. There are big differences in the strength and ability of sustained precision on different assemblies. With weak cartridges such as.22 LR applied in light-use scenarios, a pair of skinny aluminium rings may work well, while firearms with very powerful recoil often combined with a heavy sight may require steel rings or thicker aluminum rings with recoil lugs to be used.

Sizes

Scopes for ring mounts are available in many different sizes. The most common ones are:
  • 1 inch
  • 30 mm
  • 34 mm
Some less common standards are:
  • 26 mm – Some older European scopes
  • 35 mm – Some IOR, Vortex and Leupold models
  • 36 mm – Some Zeiss and Hensoldt models
  • 40 mm – Some IOR models and Swarovski dS

    Lapping

For a ring assembly to grip evenly, it is important that the scope rings are circular and coaxial with the scope tube. On ring mounts that grip unevenly, the ring mount can be lapped to prevent uneven pressure when mounting. One scopes made for ring mounts, it is not uncommon to get ring marks when mounting the rings.

Ring inserts

There are insert rings on the market which allows for mounting a scope inside a ring mount of a larger diameter. An example could be to mount a scope with a 1-inch tube in a 30 mm mount using a plastic insert.
There are also special ring mounts in the market with circularly shaped ring inserts made to provide stress free mounting without lapping, with Burris Signature Rings and Sako Optilock Rings as two well-known examples. Burris Signature was introduced in 1995. A patent was applied for in 1994, and was granted in 1995. Sako Optilock has been sold since some time in the early 2000s. The trade name Optilock was registered in the US in December 1997, and has been marketed in the US since December 2001. In 2000, Sako was sold to Beretta Holding. In 2002, Burris was also sold to Beretta Holding, and thus Burris and Sako got the same owners. Burris' original patent for the rings with the circular insertes was considered to have expired in 2014, and as of 2020 is listed as "definitely expired".
In 2015, XTR Signature Rings was launched as a further development of the Burris Signature series. The XTR variant differs in that it has two circular cavities per ring assembly versus one. A patent for the XTR Signature Rings was applied for in 2016, and was granted to Burris in 2019.

Mounts for compact sights

Many reflex sights and holographic sights have proprietary mounts.
  • Aimpoint Acro rail: A dovetail rail for attaching a sight via a clamping mechanism, and with a 4 mm wide straight recoil lug groove. The dovetail is approximately 16.5 mm wide, and is radiused so as not to have any sharp edges. The mount is compact enough to be used on pistols, as well as rifles and shotguns. Launched in 2019 together with the sights Aimpoint Acro P-1 and C-1. Also used on Aimpoint Acro C-2 and P-2, as well as Steiner MPS.
  • Aimpoint Micro standard: First introduced in 2007 on the small tube sight variants of Aimpoint, but today used by other manufacturers as well. Popular on rifles and shotguns, but not on handguns due to its size. The mounting standard uses four screws and one cross slot acting as a recoil lug. Used on red dot sights such as Aimpoint Micro, Vortex Crossfire, Sig Sauer Romeo 4 & 5, and some Holosun Paralow variants.
  • Aimpoint CompM4 mount: Launched in 2007 with the Aimpoint CompM4 sight. The sight is attached to the mount via two M5 screws from the underside, and the mount has a transverse groove acting as a recoil lug. The Aimpoint Comp line was launched in 1993. The predecessor of the CompM4, CompM2, had a 30 mm ring mount and was introduced in the American military in 2000. Some manufacturers have copied the M4 mount system, but it has mainly been used by Aimpoint.
  • C-More standard: A mounting standard introduced by C-More Sights. Uses two screws and two circular notches acting as recoil lugs. Used on red dot sights such as Delta Optical MiniDot, Kahles Helia, Vortex Razor and Sig Sauer Romeo3.
  • Docter/Noblex standard: The mounting pattern which through the 2010s was used by the largest number of manufacturers, perhaps due to the wide range of aftermarket mounts available. The mounting standard uses two screws and four circular notches acting as recoil lugs. Used on red dot sights such as Docter/Noblex sights, Burris Fastfire, Vortex Viper, Leica Tempus, etc.
  • Shield standard: A proprietary standard used by Shield Sights. Similar in shape to the Noblex/Docter footprint, but with other dimensions. In addition to the Shield red dot sights, it is also used on the Leupold Delta Point Pro.
  • Trijicon RMR/SRO-standard: Has two screw holes, and two shallow circular notches acting as recoil lugs. Mainly used on the Trijicon RMR and SRO red dot sights, as well as on some Holosun sights.
  • Other: Some notable red dot sights which have unique footprints not compatible with any of the above are Sig Sauer Romeo 1, Holosun Paralow 403A, Holosun 509T and Swampfox Kraken MRDS. There also exists reflex sights for ring mounts or with an integrated Picatinny base.

    Link between scope and firearm

Bases

By bases, is usually meant an interconnecting part between the scope and the firearm. For example, a base may have a picatinny attachment on the underside, while the upper side may have either a ring or rail mounting. On some assemblies, the upper and lower parts of the base are separate parts that must be screwed together and fastened to a specified torque. A base can thus sometimes constitute a complete scope mount assembly, but is most often used to refer to the lower part of a two-part scope mount assembly.
The firearm interface which sits on the firearm and to which the scope mount is attached is often called the base or rail.
Some types of bases are:
;Standard mounts:
  • Picatinny rail: Standardized slot distances.
  • Weaver rail: Varying width between the slots.
;Proprietary and brand specific mounts:
  • Claw mount. Several types, for example Suhl Claw Mounts, Ziegler ZP mount, and others.
  • Pivot mount. Several types, for example EAW, MAKlick, Steyr Luxus, and others.
  • Aimpoint Micro, also used by other red dot manufacturers..
  • Blaser saddle mount
  • Contessa 12 mm "Euro rail" mount
  • Browning X-Lock
  • Double dovetail, which is rotated and tapped into place. Several types, for example the Leupold Dual Dovetail
  • Mauser M03 Double Square Mount
  • Picatinny-against-picatinny
  • Pulsar type rail mount. Has some visual similarities with the Zeiss rail, but is incompatible due to a wider base and steeper angle.
  • Redfield type with windage adjustable mount, also known Redfield Standard Junior. Similar concepts are made by other manufacturers, e.g. "Leupold standard", "Burris TU/SU". Also manufactured by Weaver. Specifications can vary between manufacturers.
  • Ruger integral type
  • Sako Optilock, either with rings separate from the bases, or with rings as part of the bases. Bases come in various variantes to fit either Sako tapered dovetail rail, Tikka straight dovetail, Weaver or Picatinny.
  • Sako tapered dovetail rail
  • Sauer ISI mount
  • Sauer SUM mount
  • Schultz & Larsen integral Slide & Lock type
  • "STANAG" Claw Mount, used on FN FAL, HK G3, HK33, G3SG/1 and MP5. Most STANAG bases must be used with corresponding STANAG rings, but there are also STANAG bases for scopes with rails.
  • Dovetail rail. The flank angle varies, and dovetail rail mounts may therefore be regarded as non-standardized, even for a given witdth.
  • Trijicon ACOG/VCOG rail