Does the Holosun HE510C-GR Fit a RMSc Footprint?
By Amis Thains Published 6 min read
As an Amazon Associate we earn from qualifying purchases, at no cost to you.
On this page (7 sections)
You are checking a mount spec sheet for the Holosun HE510C-GR and wondering if it drops straight into your existing Shield RMSc base or keymod slot. This page tells you exactly how the footprint works, what adapters bridge the gap, and which long-gun platforms it handles well without forcing a fit.
In short: No, the Holosun HE510C-GR (and HS510C Multi-Reticle 2) does not use a Shield RMSc footprint. It is designed to mount directly to Picatinny or Weaver rails via its included rail adapter.
To use it in a RMSc keymod slot or plate, you need a dedicated adapter base that accepts the Holosun 507 footprint and sits in the RMSc mounting interface. It is a standard rail-mounted reflex sight, not a micro-dot keymod sight.
Quick picks
Our shortlist for this job · tap one to see today's price
Monstrum’s Shrapnel base accepts the 507k footprint and mounts to Picatinny, solving the RMSc-to-rail gap in one piece.
The HE510C-GR’s 2 MOA dot, 65 MOA circle, and shake awake features cover distance shooting without extra magnification.
What a RMSc Footprint Is and Why the 510C Does Not Match It
The Shield RMSc footprint is a small, recessed keymod or plate pattern used on micro-dots like the 510t and 502t. It is shallow and tight, designed for compact pistols and AR-15s where space is at a premium. We cover best deprime tool in a guide of its own.
The Holosun HE510C-GR and HS510C Multi-Reticle 2 use a different mounting system. They sit on a flat Picatinny or Weaver rail via a dedicated adapter bracket that clamps the rail. The base of the sight is wider and deeper than the RMSc footprint.
You cannot drop a HE510C-GR into a RMSc keymod slot. The mounting holes, base depth, and width do not align. If your setup has a RMSc plate or keymod window, you need an adapter that accepts the Holosun 507/510 footprint and mounts to the RMSc interface.
The Monstrum Shrapnel base accepts the 507k footprint and mounts to Picatinny, letting you use the 510C where a RMSc base was planned.
- Mount adapter for direct mounting of Shield RMS, RMSc, 407k, and 507k standard red dots
- Available in either Venom/Docter, RMR, or Shield RMS/RMSc/407k/507k standard footprint
How the HE510C-GR Actually Mounts on Long Guns
Out of the box, the HE510C-GR includes a Picatinny or Weaver rail adapter. You clamp the sight to the rail, set it square, and tighten the set screws. That is the whole process for most rifles, shotguns, and air rifles.
The sight sits close to the rail because it is a reflex design, not a magnified scope. You get a 2 MOA dot, a 65 MOA circle, or both, depending on which reticle mode you select. The solar failsafe keeps the battery topped off in daylight, and shake awake turns the unit on with movement.
For long guns, the key advantage is speed. You see the reticle immediately when you raise the rifle to your shoulder. No focus, no diopter adjustment needed for most shooters because the reticle is projected at infinity.
The Multi-Reticle 2 sight gives you the dot, circle, and combo needed for zeroing on long guns without swapping lenses.
- Multi-Reticle System (MRS): Choose between a 2 MOA dot, 65 MOA circle, or a circle-dot
- Solar Failsafe: Continuous operation powered by solar energy when ambient light is
When the RMSc Question Really Matters
You will hit this question if you are building a rig that mixes a RMSc keymod plate with a full-size reflex sight. It happens on some AR-10 platforms, compact .22 rifles, and shotgun chassis where the top plate has a RMSc window instead of a full Picatinny rail. We cover cvlife 3-9x40 optics r4 reticle crosshair scope review in a guide of its own.
The fix is an adapter plate, not a different sight. A RMSc-to-Picatinny riser or a dedicated Holosun 507-to-RMSc adapter fills the gap. The sight still uses its standard rail mount; the adapter just changes the interface.
If you are putting the HE510C-GR on a Marlin 45-70 or a shotgun, you are almost certainly using a full Picatinny rail. The RMSc footprint is rare on those platforms. Confirm your rail type before buying an adapter.
Pro tip: Check whether your top plate has a full Picatinny rail or a recessed RMSc window. Most lever actions and shotguns use full rails, which the HE510C-GR mounts to directly.
Common Myths About the 510C Footprint and Fit
Myth: The HE510C-GR fits any micro-dot keymod slot. Fact: It does not. The 510C base is sized for Picatinny or Weaver rails. Micro-dot keymod slots are too shallow and narrow for the 510C mounting bracket.
Myth: You need a special Holosun RMSc adapter from the factory. Fact: Third-party adapters work. A Picatinny-to-RMSc riser or a 507-to-RMSc plate accepts the sight’s standard bracket and bolts into the RMSc interface.
Myth: The sight will not zero on a 45-70 or shotgun. Fact: It zeros the same as any reflex sight. The 2 MOA dot and 65 MOA circle are large enough to see at 25 to 100 yards, which covers most hunting and sport shooting ranges for those platforms. The other half of this decision is getting rifle scope model:2.5-10x40e/gcx8011 right.
What the HE510C-GR Does Well on Long Guns
The sight is built for speed and simplicity. On a Marlin 45-70, a Remington 870, or a .22 rifle, you get a large, bright reticle that is easy to acquire without flipping a switch. The solar panel on the side keeps the unit charged during outdoor shooting, which matters if you are in the field for hours.
The shake awake feature saves battery life by turning the sight on when you move it. You do not have to flip a switch every time you shoulder the rifle. This is a small detail that adds up over a season of hunting or trap shooting.
The MRS reticle gives you three options: a 2 MOA dot for close range, a 65 MOA circle for medium distance, or the combo for all-around use. You cycle through them with the selector switch on the left side of the housing.
The OPD protective case covers the HE510C-GR when it is not on the gun, shielding the lens from scratches and dirt in the field.
- Protective Case Scope Cover For HoloSun HS510c and HE510c-GR Elite
- Easy to put on and remove. The covers fits the Holosun HS510C.
The bottom line
The Holosun HE510C-GR does not use a RMSc footprint. It mounts to Picatinny or Weaver rails via its included adapter. If your platform has a RMSc keymod window, buy a third-party 507-to-RMSc adapter plate and the sight will work without modification. Most readers mounting it on a lever action, shotgun, or .22 rail can skip the adapter entirely and clamp the sight straight to the rail.
- Mount adapter for direct mounting of Shield RMS, RMSc, 407k, and 507k standard red dots
- Available in either Venom/Docter, RMR, or Shield RMS/RMSc/407k/507k standard footprint
Frequently asked questions
Can I mount the Holosun HE510C-GR on a RMSc keymod slot?
Not directly. The 510C base is too large and deep for a RMSc keymod window. You need an adapter plate that accepts the Holosun 507 footprint and mounts into the RMSc interface. A Picatinny-to-RMSc riser also works if the window has enough depth.
Does the HE510C-GR work on a Marlin 45-70?
Yes, if the 45-70 has a Picatinny rail on the receiver or a drilled-and-tapped top with a rail adapter. The sight clamps to the rail like any reflex unit. The 2 MOA dot and 65 MOA circle are visible at 25 to 100 yards, which covers most 45-70 shooting distances.
What is the difference between the HE510C-GR and the HS510C Multi-Reticle 2?
The HE510C-GR is the grey anodized version of the HS510C Multi-Reticle 2. The internal optics, reticle options, and mounting interface are the same. The only real difference is the finish color. If you see both in a shop, they perform identically.
Do I need a magnifier for the HE510C-GR on a long gun?
For hunting or sport shooting out to 100 yards, no. The 2 MOA dot and 65 MOA circle are large enough to see without extra magnification. If you are engaging targets past 200 yards, a 1.5x to 3x magnifier behind the reflex sight can help, but it adds length and weight to the platform.
Where can I buy the Holosun HE510C-GR?
The sight is available through online gun stores like Primary Arms and through major outdoor retailers. It is also stocked on Amazon. Check the current seller listing for the included rail adapter and battery, because some listings sell the sight without the mounting bracket.