In this guide, we will explain the footprint and mounting of the Holosun 407K and 507K red dots so you can be sure that they are compatible with your pistol. Red dots are not made to a particular industry standard, so it is important to know which red dot is compatible with the handgun you want to use it with.
The Holosun 407K and 507K are part of Holosun’s “K” series of red dots. They both have the same dimensions, with the only difference being the type of reticle.
We will cover what to look for on your existing handgun and the specifics of the Holosun 407K and 507K mounting footprint.
Optics Ready Handgun
First, your handgun must be optics ready to mount a red dot to the slide. Handguns that are optics ready typically come with cover plate on the slide near the rear sight. This cover plate covers the red dot mounting surface when a red dot is not being used. In some cases, the cover plate may include the rear sight.
In the picture below the two handguns on the left are optics ready, while the handgun on the right is not.
The mounting pattern that is machined into the handgun slide for the red dot is called the mounting “footprint”. This footprint is not an industry standard and can vary between handguns and red dots. Check the manual that came with your handgun for details on how to remove the cover plate and what red dot footprint your handgun has. Also compare it to our photos below.
Handgun Size
Next, it is important to understand if your handgun has a “full-size” slide or a “compact” or “slim” slide.
Full size handguns typically have a slide that is about 1.0 to 1.1 inches wide. Some examples are the Glock 19, Walther PDP, and Sig Sauer P320.
Compact size handguns typically have a slide that is about 0.8 to 0.9 inches wide. Some examples are the Sig Sauer P365, Glock 43X MOS, and the Springfield Hellcat.
In the picture below, the handgun on the left is full size (Walther PDP), and the handgun on the right is a compact (Sig P365).
The Holosun 407K and 507K are compact red dots intended for smaller compact handguns. If you have a full-size handgun, consider the Holosun 407C or 507C instead.
The Holosun 407K and 507K Mounting Footprint
The Holosun 407K and 507K has Holosun’s “K” mounting footprint. This footprint is similar to the popular RMSc (or Shield) footprint. The RMSc footprint has four posts, one in each corner, and two screw holes near the rear of the sight.
The Holosun K is the same except the rear posts have been removed and the front posts are shorter.
In the picture below, you can see the footprint on the Holosun 407K and 507K.
In general, handguns that are compatible with the Holosun “K” footprint are also compatible with the RMSc footprint. However, not all handguns with the RMSc footprint are compatible with the Holosun K Footprint.
Some handguns like the Sig Sauer P365, Ruger Max-9, S&W Equalizer, and the FN Reflex MRD have slides that are compatible with both the Holosun K footprint and the RMSc footprint. The Holosun 407K and 507K will mount directly to these handguns without an adapter plate.
The picture below shows the Sig P365 slide that is both “K” and RMSc footprint compatible.
Other handguns like the Springfield Hellcat, Glock 43X and 48 MOS, S&W M&P Shield, and the Walther PPS are only compatible with the RMSc footprint. In these cases, an adapter plate must be used to mount this optic to these handguns since the rear posts are present.
The picture below shows the Springfield Hellcat Pro footprint. Notice the four posts in the corners. This makes this handgun not compatible with the Holosun “K” footprint.
We recommend the following adapter plates to mount this optic to these handguns:
Will the Holosun 407K and 507K Fit your Handgun?
The Holosun 407K and 507K will fit any compact handgun that is optics ready and has a compatible Holosun K footprint. Some handguns that are RMSc footprint compatible may not be Holosun K footprint compatible and require an adapter plate as noted above.