Hey internet friend, today we are going to discuss which red dot sights (and green dots) will fit the Sig P320, M17, and M18 as long as they have the Romeo 1 Pro cut slide. The optics we cover in this article will all mount directly on the slide and won’t require any additional adapter plates or screws.
Note: If you have an older Sig P320 with a Romeo 1 cut slide these won’t work. But if your Sig P320, M17, M18 is optics ready and made after 2019 then you likely have the Romeo 1 Pro cut.
Here is a pic to show what a Romeo 1 Pro Cut slide looks like. It will have a curved front.
Anyway, fun fact, the Romeo 1 Pro cut slide is actually a Delta Point Pro footprint, a.k.a DPP Footprint.
So this means any DPP Footprint optic will fit on your Romeo 1 Pro cut Sig P320, M17, or M18 .. hooray!
So with that being said, here are some of the best optics you can mount directly on your Sig P320, M17, or M18 optics ready model. These will mount directly on your slide and won’t require any adapter plates (as long as you have the romeo 1 pro cut slide!)
Key Takeaways
Here is a summary of all the optics we will be recommending, scroll down to learn more about each.
- Sig Romeo X Pro Series – these optics are offered in an open reflex or closed emitter version and multiple reticle versions. They are going to give you the lowest deck height which will allow you to use your low iron sights on your Sig P320 and their rear dovetails will act as rear dovetail sights for your Sig M17 or M18 when you remove your cover plate.
- Holosun SCS 320 – this is a solar recharging optic that comes with a green mutli-reticle system. It’s an enclosed emitter and a great option if you want something enclosed, with a multi reticle system, and with a green reticle.
- Vortex Defender Series – there is the Defender ST and Defender XL. These are great options if you are looking for a great all around optic. Something reliable with an unbeatable warranty. These optics come in red dot reticles only. The Defender ST is great for everyday use, and the Defender XL has a very large window for competition shooting.
- Primary Arms GLX RS-15 – the RS-15 comes in a 3.5 MOA dot or an ACSS Vulcan Reticle. This is an excellent option if you want the benefits of the ACSS Vulcan reticle such as quicker red dot acquisition and that extra “aim assist” the ACSS Vulcan reticle gives you.
- EoTech EFLX – This is not a bad option, it’s main strength is that it comes in an FDE version as well as a black housing version. It’s a solid optic, however it doesn’t have auto on/off like others mentioned here.
- Leupold Delta Point Pro – This is the oldest pistol optic in this list. It also has the highest deck height, so even if you had tall iron sights, they may not be visible through this optic. The Leupold Delta Point Pro has a large window and many use it for competition shooting or everyday use. The brightness button on the optic can be a bit of a hassle but it also has an auto brightness mode.
Sig Romeo-X Pro Series – Best if you Value Co-Witnessing
The Sig Romeo X Pro and Sig Romeo X Enclosed Pro are two of the latest pistol optics from Sig. Sig is really stepping up their game when it comes to Pistol Optics and they are taking notes from Holosun.
There are quite a few options to choose from in this series, however the offering is simple. Sig makes the Romeo X Pro and the Romeo X Pro Enclosed. One is an open emitter and one is a closed emitter design. The closed emitter is more expensive, but also offers more protection against debris, dust, and precipitation.
Both the Romeo X Pro and Romeo X Enclosed Pro optics have 7075 aluminum housings, side mounted batteries, auto on/off, and around 20k hours of battery life. These also come with 12 daylight brightness settings, and 3 nightvision settings.
Both the open and closed emitter versions are offered in a 3 MOA version, 6 MOA version, or a version which has a multi reticle with a 32 MOA outer circle, and 2 MOA center dot.
Lastly, but possibly one of the most important features of the Sig Romeo X Series of optics is it’s low deck height. Since the battery is side mounted, the deck height is super low on this optic. It’s the lowest out of any Delta Point Pro footprint optic in this list and on the market. So what tha means is that you can co-witness your low iron sights on your Sig P320 platform. The other nice thing is that if you have a Sig M18 or M17 or a P320 that loses it’s rear sights, the rear sight machined into the Romeo X Pro housing can be used as backup rear iron sights.
Holosun SCS 320 – Best Solar Recharging Option
The Holosun SCS 320 is one of the newest optics from Holosun, and also one they designed specifically for the Sig P320 platform. It’s the only Delta Point Pro footprint optic Holosun makes currently.
It’s also part of the “Solar Charging Sight” series from Holosun, which is their latest technology which incorporates solar recharging of an internally rechargeable battery. So the solar panel charges and internal battery. The reserve power a.k.a. Capacity of this battery is 20K hours. Which means if it were to see no natural or artificial light, the optic would last for 20K hours.
But what’s cool is the solar panel charges the battery faster than the battery drains. Therefore creating theoretical infinite battery life.
The SCS 320 has a 7075 T6 Aluminum housing, has auto brightness mode only, comes in a green reticle only, and has the MRS reticle which is a 32 MOA outer ring and a 2 MOA center dot.
It’s also an enclosed emitter, which means the laser emitter is protected from outside elements like dust, dirt, debris, and precipitation, ensuring nothing can get in the way of the laser emitter and glass.
This is a great choice if you want an enclosed emitter, and something you just keep on forever and never worry about adjusting brightness manually or changing batteries.
Vortex Defender ST & XL Series – Best EDC or Competition Option
The Vortex Defender series is the latest Pistol Optic offering from Vortex. If you don’t know, Vortex is famous for their industry leading customer support and warranty. They warranty all their products no matter what happens. If you smash it, break it, or if it just stops working, they have a no hassle and very quick turnaround exchange process.
With that being said, the Defender ST and Defender XL are their latest Pistol Optics. These are a solid all around choice because they have 7075 Aluminum housings, auto on/off features, decently long battery life at around 20k hours at setting 6 and have bright red reticles. It has 10 daylight brightness settings and 2 nightvision settings.
The Defender ST has a nice sized window (similar to a Trijicon RMR) and is designed for everyday carry use. It has a top mounted battery, manual brightness controls, and comes is a 3 MOA or 6 MOA Dot.
The Defender XL is made for competition shooting. It has a really large window and competes with optics such as the Holosun 507 Comp and Trijicon SRO. The Defender XL is very similar to the ST in terms of construction, it just has a much larger window, and easier to open battery tray, and comes in a 5 MOA dot or 8 MOA dot.
Primary Arms GLX RS-15 – Best ACSS Vulcan Option
Another relatively new optic to the market is the Primary Arms GLx RS-15. The RS-15 has a 7075 Aluminum housing which is great, a nice size window, a little larger than a standard pistol red dot, but smaller than a large competition window. It also has auto on/off technology, a top mounted battery, and manual brightness only with side buttons and 10 daylight and 3 nightvision modes.
Primary arms has been making red dots for a while so this is one of their latest iterations. Primary arms also has a lifetime warranty on all their products.
What makes this optic cool is it’s offered in a 3 MOA red dot version and also the ACSS Vulcan reticle. If you aren’t familiar with the ACSS Vulcan reticle, it’s a 250 MOA large outer circle, and 3 MOA center dot. The large outer ring is only visible when you need to adjust your aim, this helps you “find the dot” fast.
Lastly, the RS-15 has a .5 MOA click adjustment. Which is the most precise aiming adjustment in this category of pistol optics. Most other brands have 1 MOA and sometimes 1.5 MOA. Since these are pistol optics you may not need that much precision, but it’s worth noting.
The ACSS Version is more expensive and consumes more battery, it’s rated at about 5K hours of battery life, while the 3 MOA version is rated at 25K-50K hours of battery life. The outer ACSS Vulcan ring can also be toggled off which would save battery life if that was a concern.
Eotech EFLX – Best Alternate FDE Option
The EoTech EFLX could be a decent option for you if you are an EoTech Loyalist or if you really want a red dot in an FDE color. The EoTech EFLX isn’t a bad pistol optic in anyway, it is however lacking in some features, such as auto on/off technology.
The EFLX has a 10 year warranty. It has manual brightness modes only and the window size and size of the optic is meant for normal everyday use.
It’s available in an FDE or black housing color, and comes in a 3 MOA red dot or 6 MOA red dot. Battery life is rated at 20-25k hours on setting 5. It has 8 daylight and 1 nightvision setting.
EoTech doesn’t list the housing material or waterproof ratings. We are sure it’s either 6061 or 7075 aluminum and waterproof for your needs, but it’s something worth noting.
Leupold Delta Point Pro
The Leupold Delta Point Pro is the oldest pistol optic on this list. It’s been around the longest, and has the most proven track record. Leupold has a lifetime warranty on their products, similar to Vortex.
With that being said, this optic can be a bit confusing. The first and most important thing to know is that this optic has a larger style window. It’s not as big as the Defender XL, but it’s big enough to be used in competition shooting – many people do use it.
It does have auto on/off technology and a top mounted battery, it also has a steel shroud that protects the aluminum window housing.. The biggest downsides to this optic are the lack of specs listed by Leupold and also the deck height. It has the highest deck height out of any optics in this list. We also don’t know what it’s waterproof ratings or housing material are, however we are sure they are strong and good.
The Leupold Delta Point Pro comes in a few models. Mainly it is available in either a Black Housing or FDE housing color. Second it is available in a 2.5 MOA dot version, a 6 MOA dot version, and has another version that features additional night vision modes.
The Delta Point Pro has an automatic brightness feature, and also manual brightness modes, however the manual brightness modes are a little more clunky to use than others as it has only one button mounted towards the inside of the window, vs on the side like many others. This can be frustrating because you have to cycle brightness modes linearly all the way up, then all the way down, and due to the placement of it, your finger can hit the inside of the glass and smudge it.
Conclusion
Overall you can see there are quite a few options for the Sig P320, M17, and M18. We feel the strongest offerings are going to be from Sig, Holosun, and Vortex. The Primary Arms RS-15 is an up and comer and would be a great option if you really wanted the ACSS Vulcan reticle.
The Sig is the most ideal due to the fact it lets you co-witness your iron sights, but it’s also one of the most expensive. A great alternative to the Sig is going to be the Holosun SCS 320 if you want an enclosed emitter and also a Multi Reticle System. If you are ok with a red dot only then we think the Vortex provides the best budget friendly options.
Anyway regardless of which item you go with, you can’t go wrong with any of the optics we listed here.
At Optics Ready we only carry items we would use personally and the optics mentioned here are no exception.
We hope you found this article helpful.
Thank you for reading!
