In this guide, we will explain the footprint and mounting of the Holosun 509T so you can be sure that it is 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.
We will cover what to look for on your existing handgun and the specifics of the Holosun 509T 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 handgun on the left is 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) with the Holosun 509T, and the handgun on the right is a compact (Springfield Hellcat) with the smaller Holosun 507K.
The Holosun 509T is a full-size red dot intended for handguns with a full-size slide. If you have a compact size handgun, consider the Holosun EPS Carry or 507K instead.
The Holosun 509T Mounting Footprint
The Holosun 509T has a unique mounting footprint with a rail and an opposing clamp similar to (but different from) a standard picatinny rail mount. It also includes an adapter plate for the more common RMR footprint.
In the picture below, you can see the footprint on the Holosun 509T and the included RMR adapter plate.
While it seems very similar to the Aimpoint Acro footprint, it is different and is not cross compatible.
In the picture below, the 509T is on the left and an Aimpoint Acro footprint red dot is on the right.
Currently, there are no full-size optics ready handguns available with this unique “509T” footprint. However, the included adapter plate allows this optic to mount to any handgun with an RMR footprint.
The picture below shows the Holosun 509T with the adapter plate and a handgun with an RMR footprint.
Many full size optics ready handguns like the Glock MOS and Walther PDP have proprietary footprints that require adapter plates. Some come with adapter plates included, while others must be ordered separately.
For example, The Glock 19 MOS handgun comes with an RMR adapter plate, so this optic will work with it. The Walther PDP does not come with any adapter plates, but they can be ordered directly from Walther (the first one is free). Simply select the “509T” plate when ordering.
Note that if your handgun requires an adapter plate to convert it to an RMR footprint, you will need to use the included adapter plate also to mount the Holosun 509T as shown below.
Note that the included adapter plate requires additional screws to attach it to the slide before mounting the optic. If your handgun requires an adapter plate for the RMR footprint, this will result in using two adapter plates, both with screws attaching them to the next. We recommend using only one adapter plate, if possible, to eliminate failure points and to allow the optic to sit lower on the slide.
To eliminate the need for using two adapter plates, we have the following adapter plates available that will allow the Holosun 509T Optic to mount to these handguns with only one plate:
- HK VP9 – 509T Adapter Plate
- CZ P10 – 509T Adapter Plate
- FN 509 – 509T Adapter Plate
- Sig P320 – 509T Adapter Plate
- S&W M2.0 – 509T Adapter Plate
- Walther PDP 1.0 – 509T Adapter Plate
Will the Holosun 509T Fit your Handgun?
The Holosun 509T will fit any handgun that is optics ready and has an RMR compatible footprint. Handguns with an RMR footprint will require using the included adapter plate.
If your handgun does not have a RMR footprint already milled into the slide, consider one of the adapter plates above.