Luckily, mounting pattern standardization keeps things simple.

With lever-action rifles regaining popularity in the field, hunters of all ages are looking for alternatives to “as-issued” open sights. They’re adopting red dot sights as a pragmatic solution that even us purists can get behind.

(Related Content: What is a Red Dot Sight, and Why Do So Many Lever-Action Rifle Hunters Love Them?)

With so much demand, there comes a seemingly never-ending supply. Which is great for us who enjoy having plenty of red dot sight options to choose from. But what about getting them atop our favorite lever guns? We also need to consider the mount (or mounting plate, or adaptor), and with that, compatibility with the red dot optic.

Luckily, there are simple mounting standards to help us along the way. And to keep things even simpler, we’re focusing on just two of those mounting standards – the Docter/Noblex mounting standard, and the Trijicon RMR mounting standard. Why Docter/Noblex and Trijicon RMR? Because these mounting standards accommodate the greatest variety of red dot sights, specifically the “exposed reflex” variety. Which brings us to a side note: when we say “red dot” in this article we’re referring to exposed reflex sights. This variety of red dot is especially popular with lever gun hunters.

But first, a few definitions.

What is a red dot sight mounting surface?

The entire top of your red dot sight mount (i.e., the part not affixed to your firearm) is referred to as the mounting surface. The mounting surface is machined with holes to accept mounting screws from your chosen red dot sight, as well as pins to mate to your optic’s pin sockets.

Example of a red dot sight mounting surface, with a Docter/Noblex standard mount for a Winchester 1886 receiver on the left and relevant distances on the right.

What is a red dot sight footprint?

The entire bottom surface of the red dot sight is referred to as the footprint. The footprint is machined with holes to pass mounting screws to your chosen mount, as well as sockets to accept your mount’s pins.

Examples of red dot sight footprints, representing two different footprint standards.

What is a red dot sight mounting standard?

The arrangement of the screw holes and pin sockets in a red sight’s footprint form a pattern with certain dimensions. This pattern with its specified locations and distances is referred to as the mounting standard. Different red dot footprints can feature the exact same pattern of holes and sockets. Therefore, those sights are of the same mounting standard. So for example, two different red dot makes/models can be swapped out on the same mount (in our case, a rifle receiver mount or a rifle barrel mount), as long as the footprints and mounting surface feature the same mounting standard.

(Related: purchase Red Dot sight mounts by Turnbull Restoration)

Now for the fun stuff: Docter/Noblex and Trijicon RMR mounting standards.

Doctor/Noblex mounting standard – description and compatible red dot sights:

The most common red dot footprint conforms to the mounting pattern known as the Docter/Noblex standard. Sights featuring this footprint contain two holes for mounting screws and four sockets to accommodate the mounting surface’s four corner pins. The Docter/Noblex standard’s mounting pattern is easy to use and reliable. Some of the most popular red sights featuring this footprint are Vortex Venom, Vortex Viper and Burris FastFire 3.

  • ADE Advanced Optics RD3-006B Huracan
  • ADE Advanced Optics RD3-009 Crusader
  • ADE Advanced Optics RD3-012 Delta
  • ADE Advanced Optics RD3-013 Bertrillium
  • ADE Advanced Optics RD3-015 Zantitium
  • Athlon Midas TSR1
  • Burris Fastfire 2
  • Burris Fastfire 3
  • Delta Optical MiniDot
  • Delta Optical MiniDot II
  • Docter Sight C
  • Docter Sight II Plus
  • Docter Sight III
  • Docter QUICKsight 5.0 VR
  • Hawke Reflex 1×25
  • Leica Tempus
  • MAKdot 1×25
  • Noblex Sight C
  • Noblex Sight 2 Plus
  • Noblex Sight III
  • Noblex Sight G
  • Noblex QUICKsight 5.0 VR
  • Sightmark Mini Shot M-Spec
  • Sightmark Mini Shot Pro Spec
  • US Optics DRS 2.0
  • US Optics DRS 2.0 Enhanced
  • Vector Optics Frenzy 1x20x28
  • Vomz Pilad 1×20
  • Vortex Viper
  • Vortex Venom

(Source: Optics-Info.com)

Trijicon RMR mounting standard – description and compatible red dot sights:

This mounting standard’s namesake is the hugely popular Trijicon RMR (Ruggedized Miniature Reflex) Sight. This red dot sight’s footprint includes two holes for mounting screws and two sockets to accommodate the mounting surface’s two pins which are on the front corners. Along with the Trijicon RMR and SRO, this standard accommodates popular red dot sights from Holoson, ADE Advanced Optics and more.

  • Trijicon RMR
  • Trijicon SRO
  • Holosun 407C
  • Holosun 407C V2
  • Holosun 407C X2
  • Holosun 507C
  • Holosun 507C V2
  • Holosun 507C X2
  • Holosun 508T
  • Holosun 508T X2
  • Riton X3 Tactix PRD
  • NcStar VISM FlipDot Pro
  • ADE Advanced Optics RD3-011 Avenger
  • ADE Advanced Optics RD3-019 Stingray
  • ADE Advanced Optics RD3-020 Raptor
  • ADE Advanced Optics RD3-023 Valkyrie
  • Swampox Kingslayer 1×22
  • Swampfox Liberty RMR 1×22
  • Swampfox Justice RMR 1×27
  • Vector Optics Frenzy 1x22x26

(Source: Optics-Info.com)

All in all, pretty straight-forward stuff. If you have any questions, or if you’d like to share you thoughts and experiences, feel free to comment below.