Apex Optic Mount for ACRO/MPS* – Sig P320 RX and RX Pro

If you’ve got a Sig P320 with the RX or RX Pro slide cut and want to mount an Aimpoint ACRO or Steiner MPS, you’ve probably run into the same problem a lot of our customers have: the optic just doesn’t want to lock in tight. That’s where this steel mount comes in. It replaces the factory plastic plate to give you a rock-solid base that actually lets the ACRO locking bar fully engage. No more worrying about the optic walking loose under recoil or after a few hundred rounds downrange. It’s a simple fix for a common headache.

Will this fit my gun?

This mount is designed specifically for Sig P320 pistols with the RX Classic cut or RX Pro cut slide. Here’s what fits:

• Sig Sauer P320 RX (with factory optic-ready slide)
• Sig Sauer P320 RX Pro
• Works with factory Loaded Chamber Indicator (LCI) – no modifications needed

Optics that work with this mount:

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

Important: This mount is for the original RX/RX Pro slide cut. If your P320 slide has the newer rev2 cut (look for “-R2” in the SKU), you’ll need part #112-009 instead.

Key features

• Machined from billet steel with a black oxide finish – holds up to heavy use
• Includes Optic Sub Plate so the ACRO locking bar fully engages, preventing the optic from walking
• Direct replacement for the factory plastic plate – uses the same screws
• Retains full function of the factory Loaded Chamber Indicator
• Model-specific design – not a one-size-fits-all solution

Install difficulty: 2 out of 5

This is a straightforward swap for anyone who’s comfortable with a screwdriver. You’ll need a small Torx bit (T10 or T15, depending on your slide) and a little thread locker (blue Loctite is fine). Plan on 10-15 minutes in your workshop or at the kitchen table. If you haven’t done it before, we’ve got a quick install video on our site that walks you through it step-by-step.

Frequently asked questions

Will this work with my P320 M17 or M18?

Only if you have the RX or RX Pro slide cut. The military M17/M18 slides use a different optic footprint, so this mount won’t fit those. Check the underside of your slide – if it says “RX” or “RX Pro,” you’re good.

Do I need any extra parts to install this?

Nope. The mount comes complete with the steel plate and the Optic Sub Plate. You’ll reuse the screws from your factory plate or the ones that came with your optic. We do recommend using a dab of blue thread locker on the screws to keep everything snug.

Why can’t I just use the factory plastic plate?

You can, but the factory plate is plastic and doesn’t allow the ACRO locking bar to fully engage. Over time, especially with heavy use, the optic can start to shift. This steel mount solves that by giving the locking bar a solid, machined surface to grab onto.

Shipping: We ship from our shop in central Texas within 1-2 business days. Warranty: This mount is backed by the manufacturer’s warranty – if you have any issues with fit or function, just give us a shout. We’re a family shop and we stand behind what we sell.