Apex Optic Mount for ACRO/MPS* – Sig P320 Sig-LOC Slide Cut including M17 / M18 Models

If you’ve got a Sig P320 with the newer R2 slide cut and you’re looking to mount an enclosed optic like the Aimpoint ACRO or Steiner MPS, you’ve probably noticed that direct mounting can be a bit fussy. This mount from the kit solves that problem cleanly. It’s a precision-machined adapter that gives you a solid, repeatable mounting surface for these optics, and it keeps the optic from shifting under recoil. Plus, if you choose the version with the integrated rear sight, that sight doubles as a gas shield to keep carbon and crud off your lens—handy if you shoot suppressed or run a lot of rounds in a session.

Will this fit my gun?

This mount is made specifically for Sig P320 slides that have the factory R2 cut. That includes:

• Sig Sauer P320 Legion (R2 cut models)
• Sig Sauer P320 M17
• Sig Sauer P320 M18
• Other P320 models with the R2 slide cut

Optics that work with this mount:

• Aimpoint ACRO P-1 & P-2
• Steiner MPS
• Lead & Steel Pandora PB-3

Key features

• Secure fit: Designed to match the R2 cut exactly—no shims or filing needed
• Integrated rear sight option: Acts as a gas shield to keep your optic window cleaner, and co-witnesses in the bottom 25% of the optic window (requires a tall front sight)
• Two sight height options: Pick based on your barrel length so your point of aim matches point of impact at 15 yards with 124 gr. NATO ammo
• Works with Loaded Chamber Indicator: No need to remove or modify the factory LCI
• Includes all necessary hardware: Comes with screws and instructions

Install difficulty: 2 out of 5

This is a straightforward install. You’ll need a small Torx driver (T10 or T15, depending on the screws) and a little blue Loctite. If you’ve ever mounted an optic to a pistol slide, you can handle this in about 10 minutes. The mount indexes into the R2 cut, so alignment is automatic. We recommend watching the install video on our product page before you start—it’s short and shows the whole process.

Frequently asked questions

Will this mount work on a standard P320 with the older slide cut?

No, this mount is specifically for the R2 cut. If your slide has the older “Deltapoint Pro” footprint, you’ll need a different adapter. Check the underside of your slide—if you see the R2 cut pattern, you’re good to go.

Do I need a new front sight?

If you get the version with the integrated rear sight, yes—you’ll need a tall front sight to get a proper co-witness. We sell two height options: one for standard-length slides and one for longer barrels (like the Legion). Pick the one that matches your barrel length so your sights line up at 15 yards.

Does this mount work with the factory loaded chamber indicator?

Yes, it’s designed to clear the LCI. You don’t have to remove or modify it.

Shipping & warranty: We ship from our shop within one business day. This component comes with the manufacturer’s warranty against defects in materials and workmanship. If you have any issues, just give us a call—we’re a family-run shop and we stand behind what we sell.